BoostBrothers is actually an awesome kit, in some ways it's better than On3 (the pipe diameters for example) and it's been great to me the last few years.
The cold-side bung is for your IAT (Intake Air Temp Sensor) that you'll be pulling off of the existing airbox or cold-air-intake.
I did a write-up of instructions for the BB install on another Mustang site several years ago. Since I don't want to send those guys traffic, here it is for you as well. No major hiccups, just a few things that needed 'clearancing.' The ABS unit, the sway-bar, and making some room for the air-filter were really the only places that needed some fabrication.
0) Make sure you're running strong before you start. 36 lb. injectors, 255lph fuel pump, adjustable fuel pressure regulator, matched MAF are probably almost minimums. Adding the turbo is going to make any pre-existing problem much worse and you risk blowing the engine, get it running good before you start pulling it apart. Make sure your clutch,
tires, U-joints, brakes, timing, air-fuel ratio are all good before you start, you'll be flying when you're done.
1) Remove H-Pipe, headers, EGR system (you'll need to use a CEL eliminator of some kind or a tune to shut off the EGR), air pump and tubes (plug the heads), and stock air box/maf/intake. Grind off the "ears" that used to hold the air pump. Pull the dipstick. Disconnect the clutch cable where it enters the transmission and unbolt it from the inner fender. Pull your plugs.
2) Pierce the pan with their tool, then tap it (the front sump about 2" down between the 2nd & 3rd bolts from the front is a good spot). If you're like me they'll send you the wrong sized fitting for the drain into the pan, so you'll need to hit the hardware store for an adapter (3/8" NPT tap, 1/2" NPT fitting). Remove your oil-pressure-sending unit (it's stuck and it's 1 1/16th). Again if you're like me you have the wrong sized "T" fitting (1/8" provided, 1/4" needed). Put one together in the pipe-fitting section at the hardware store. Assemble the ends onto the braided supply line and have some band-aids handy.
3) Bolt on the turbo headers (turbo goes where your airbox was), outlets of the headers facing frontwards. I found no other way to get them on but to remove the upper intake and go from the top. I tried every angle, pulled the steering shaft, etc. Nothing else worked. You'll find the lower
radiator hose interferes with the
driver's
View attachment 122346
header, cut it where it's touching and use the supplied steel tube & clamps to piece it back together. I actually bought a longer flexible generic
radiator hose at AutoZone which cleared and didn't require cutting. You'll also find the driver's header hits the sway-bar (you'll need to fabricate some drop-mounts where it bolts to the frame-rail, mine are about 2" and I use some long carriage bolts). Since you were smart and unbolted the clutch cable while you had room, snake it around away from the heat, you have lots of room around the steering shaft since there's no more driver's exhaust pipe. You'll also need to lengthen the O2 sensor wires which will now need to reach up to the the top passenger side of the engine roughly. Cut & solder (at the harness not the sensor wires themselves) or buy some extenders.
4) You'll need to cut up the inner fender a bit for the cold-side piping from the intercooler, and as noted the radiator support (moving the hood-prop-rod-mount to the inner fender) to get a filter on. Probably also the lip on the top of the frame-rail. This is largely trial & error, have lots of cutting wheels on hand and be patient. Try really hard not to cut any wiring harnesses, check both sides before you grind.
5) Assemble (supply & drain manifolds) & Mount the turbo. You have to clock the turbo (loosen both sets of mounting bolts and rotating the compressor and turbine relative to the central bearing housing) making sure the feed line is on top and drain is on bottom, you'll use the 45 degree drain fitting on bottom, the straight one at the pan.) This is where you may have to cut the lip off the frame rail. The A/C hose that's in your way needs to be up on top of the whole turbo assembly, unbolt the mounting clips from the inner fender and bend away. Then bend again, and again, etc. While you have the room wrap it with some fireproof stuff or some silicone, it's going to get hot around there. Bolt up the rest of the exhaust components (I bought a 3"
catalytic converter to keep it legal myself). I found the bolts provided for the down-pipe to mid-pipe were too short so I picked up some longer ones. Everywhere else it's v-band clamps or band clamps, easy stuff. You'll want to use the two in-line (not side-by-side) bungs for the O2 sensors, the other will hit the A/C filter-dryer. The mid-pipe takes some pounding to get it down next to the tranny, but not bad. Mount the
air filter to the front of the turbo. I bought a "custom" one off of the
K&N website which was somewhat smaller than the one they ship. It's a tight squeeze, you'll have to move some of the headlight wiring harnesses and bend the A/C lines some more to get it to fit.
6) You're ready to attack the cold-side piping. You'll notice if you have the
ABS
View attachment 122347
unit it's going to get in the way (also in the way of the wastegate). You'll need to unbolt it and re-mount it underneath the frame rail. The lines will bend that far without removal or patching, but you'll likely need to make your own mounts as the stock mounting "frame" is too big). The piping runs off the turbo (2.5"->3" silicone sleeve), down right behind the radiator, the 180 degree elbow brings it into the driver's side of the intercooler, which snakes around into the outer fender (remove the plastic inner
wheel-well cover), and then up into the inner fender and into the
throttle body. You'll notice there's a provision for the IAT (the screw-in air temp sensor from your old intake) in the intake tubing. You'll also notice there's NO provision for your MAF! I disassembled the air-box, pulled my MAF, bought an adaptor to 3.5" tubing off of ebay along with a silicone sleeve and clamp, and cut a spot for the MAF where the tubes came together in the wheel-well. You don't want your MAF by the exhaust or turbo. I also moved the TFI (the ignition module and heat-sink mounted to the inner fender) inside the wheel-well to keep it from frying. When you go to mount the BOV you'll find the fog-lamp mount will interfere. I fabbed a new thin one (and probably saved about 10 lbs., the stocker's huge). The BOV top opening is used and goes to manifold vacuum. I was able to mount the intercooler from the bottom with no problem. Those straps they provide are for the top-mounts, which then can be bent over the
radiator support and fastened. I had to remove the power-steering-cooler (just plugging the hoses back into eachother).
7) Mount the wastegate and screamer pipe. I popped a Harley-style exhaust baffle into the screamer (1.5" x 4") which made it very civil. Don't forget that circular piece of metal which is actually the seating-surface for the wastegate valve or you'll be exhausting out the wastegate even at idle, not making full boost, etc. Ask me how I know.

You have to be careful, though, not to impede the wastegate flow too much with the baffle or you'll get boost creep (I had to open the baffle some). If you carefully moved your ABS unit you should have enough room for everything. The wastegate side-port is used (leave the top-port open to the atmosphere), which connects to the output from the turbo.
8) The stock wastegate is set for 6psi and isn't adjustable. You can swap springs or get a boost controller (which bleeds off some of the pressure to the atmosphere and therefore lets you build more boost before the wastegate opens). Dirt cheap
on ebay for manual boost controllers (though many people remove any check-balls from them because of the danger of boost spike). You'll also find you NEED a boost gauge, available almost anywhere including Autozone around here, which plumbs into the manifold vacuum. Don't start it up without one! I test-drove and found I had a bad boost controller and the wastegate was never opening! I would have blown the motor without the $40 gauge.
9) Bolt everything back together, down-gap your plugs (to prevent flame blow-out under boost) and consider a better ignition coil at minimum, a better ignition system if you have the bucks. Before start-up check all the fluids, disconnect the plug-wire at the coil and turn it over until you build up some oil pressure to prime the turbo. You'll have to do something about the PCV system to keep from pressurizing the crank-case at boost (best bet is to remove & plug it in my opinion and go to breathers -- K&N makes one that screws on in place of the oil filler cap).
10) Go for a few test drives, no boost. Make sure you're not leaking anything (oil, coolant, exhaust, etc.) and that you have no "Check Engine" light. Gently apply boost by revving (don't gun it in 1st), watch your gauge and listen for the wastegate to open if you hit around 6psi. When you drop the throttle, listen for the "hiss" of the BOV letting off pressure. Listen VERY carefully for any detonation. You'll blow your motor in seconds if you're pinging under boost. If you can make it to max boost up to redline with no hint of detonation, congratulations you've established a good base tune.
11) Have yourself professionally tuned (or DIY with a QuarterHorse or Tweecer -- happy to help you there).
12) Blow the doors of anyone who challenges you, and be careful. You have crazy power available. If you have a stock block, you probably don't want to boost more than about 10 or 12 psi even when tuned because the 5.0 tends to crack in half at >450hp. The turbo kit can easily build 15-20 psi which is ridiculous horsepower.