I to second the 268H. Grant it they are on my NPI head car, they are great mod. Not too aggressive but helps out a lot in the higher end of the powerband. No problems so far after 6,000 miles.
From my experience the cars are actually quieter down low (idle-2000rpm). Once you hit it pretty hard volume climbs pretty rapidly. But it sounds a lot cleaner thou with the LT.
The adapter plates make no difference in installing the intake. It just insures a better seal. My car ran rough the first couple days because I still did not have all my sensors. I was just trying to help.
The only thing I can think off is you have a leak somewhere. Usually if the engine idles higher the idle will jump up some. I lucked out. I did not have any issues when I did my swap. Just look around the area to make sure everything was plugged back in the right spot. Run up the rpms while...
Wait and do both. The cam swap was easier than messing with the PI intake. It took me about 4.5 hrs for the PI intake swap. If I was doing the headswap I would wait. Hate to do the job twice.
The spacer is on the old cams just transfer them over. For the bolts on the cams just go to Ford dealership and ask for the bolts that fit 01 and newer PI cams.
Yes the bolts are different. Use new bolts when the cam swap is done. Also make sure the spacer is on the new PI cams for the installation.
The Livernois kit only comes with one set of gaskets (PI). You can reuse your old ones. Just be careful when taking them off.
I like the Sportlines the best. I have them with 1/3 coil cut in the front for a better level look. You will need C/C plates. I am still on my factory shocks and struts for the past 18 months. It just looks mean from behind with my 17x10.5 bullitts and being wingless.
I went from a prochamber to the H-pipe. The volume is a lot quiter then the o/r H-pipe. The power difference is not really much. My car is basically stock except for some cams and PI intake. I am back to the H-pipe just because I like the way it sounds. (to me the H-pipe has more rumble)
I would not do it. I have 275/40 on my 10.5 bullitts and it is in my opinion too small. My next tire will be 315/35. I would just wait or just sell your old tires.
Around town I get between 20-23mpg. When I did my trip to Atlanta (Modular Powerhouse Dyno Day) I got 30 mpg. Cruise set at 75 and AC on. Rear end is stock 3.27; hopefully not for much longer.
Definetly get some 4.10s for your auto. It will help a lot. Go with a PI intake and some cams. If not do the good old headswap.
As for exhaust that is up to you. I say go with a o/r midpipe and mufflers that have the sound you are looking for.
I would stick with the 2.5" IMO. I am a fan of the MAC Flowpaths. I had Bassani, Flowmaster, and Spintech. The Flowpaths sound the best defiently with some cams.
When you switch out the heads the combustion chamber is tighter giving you a higher compression ratio. The 96-98 GT has different style of pistons compared to the 99 and newer.
I would also use no less than 91 octane with the headswap.