Well I posted this yesterday in this spot, but I guess it's not here today, so I'll try to cover everything I said yesterday.
What are some things recommended to upgrade to my 1st gen GT?
1. OK, new exhaust is a very good choice 2.5"-3" is what's recommended, no catylitic convertor if you don't have emissions
2. Air filter next good choice: K&N drop-in or cone-shaped with a Home Aid Cold Air Intake, consisting of some aluminum tubing to the filter.
3. Definately a must have is a boost controller.

Turn that boost up for minimal cost.
4. A turbo upgrade is a definate must when you have the money: T-bird upgrade is where you get the t-bird wheel and housing and replace onto the stock turbo, Charles can get you the rx-7 hybrid turbo, or the most popular is a t3/t4 turbo: you can get good ones off of buick grand nationals.
5. Suspension upgrades: I love my Ground Control coil-overs with Illumina 5-way adjustable struts.

Very spendy though.
6. If you have a lot of extra money and want the best overall mod other than a bigger turbo you can get the FE3 motor from Jahmarr Bowmann,
boostedmx6@hotmail.com, this motor hauls ass up to 7800rpms.

They love boost too.
7. Rims are always a good choice to get: General rule of thumb is 17" with 215/45 or 40 series rubber, 16" 215/ 45 or 50 series rubber, most people don't recommend 225s but they can fit with the right offset and a 40 series or 35 series rubber.
How's that? It should be pretty long. hehe