...but I just bought a 2000 GT. It's bone stock except for the MagnaFlow exhaust I had added the other day. I'd like to put about a grand into it over the next couple of months to beef it up some. Give me some suggestions.
#1: GEARS!!! If you do alot of highway driving, 3.73's.
3.90's if you have a mix of mainly highway but some city, and you still want a nice improvment.
4.10's if you dont mind higher RPM on highway driving or if you do alot of around town driving, or if you want the BEST bang for the buck.
#2: Getting a 2.5" catless mid pipe (if you can go catless, wont pass emissions test without them). X pipes make a little more power and sound more exotic. H pipes retain a little more low end tourqe and have a classic muscle car sound.
#3: Nitrous. Most hp/$ you can get. You can buy a used kit for a decent price or even some new kits with accessories for $450-800 depending on what brand and what all you get. Id reccomend a wet shot. Keep it at a 100shot and below and save youself alot of headaches.
Dont get nitrous if you are scared of breaking something though. Its hard on the engine, and alot can go wrong with it. Its all about a correct installation, and making sure the car is tuned correctly as well as being in good mechanical shape.
Keep this in mind... as you modify, each part you buy may not make a big increase, but together with other parts it can help.
For instance, dont buy a big throttle body and ported plenum and expect to feel a huge increase. Your getting alot of air in, but you havnt opened up the exhaust side of the car yet to get all that air out more efficiently... and catbacks dont count, because the real bottleneck is the stock 2.25" H pipe with 4 catalytic converters.
Hate to say it but 1k for a 4.6 powered Mustang isnt gonna get you far unless you do nitrous, or gears and a select few bolt ons.
You could most likely buy some cams and have them installed for right around a grand, but you will more than likely need to tune the car for the cams, which adds more $ on top... plus cams alone wont gain a whole whole bunch. Alot of people have good results from cams and longtube headers though.
Ontop of all though... before you sink a penny into modifying it... Go through the car and replace anything that needs replacing, change the fluids, and make sure its in good shape from the get go. Preventative matinence goes a LONG way.