I know with the older wrxs 95-00 classic shapes it was full 3" exhaust, cold air duct and a new K&N type filter for the factory airbox..... They where places to start then you would step up to ECU, Differnt Intercooler with new y pipe and turbo...... There your more big buck mods.

Some would say do handling mods like lower the car, sway bars etc....

You've got to decide where you want the car to go, and what mods you plan on doing..... if your going to go all the way you would look at the pointy end of the ECU's when purchasing....

Gives you some where to start, also find out if a full exhaust system will play around with fueling like it did with the 01's.....

Chad