Not a go-fast-mod, but I think at least as important. I have, though not yet installed, much bigger brakes for the front and disks for the rear, all from a donor '87 Galant. I got the goods from a pull-a-part place and rebuilt the calipers. I don't know yet if I'll need an adjustable proportioning valve for the rear brake pressure, though I think I probably will.
Other than that, the previous owner drilled a bunch of holes in the hood in a rectangle area above the turbo to let hot air out better (probably has at least 18hp extra now
). Lowered it with Koni shocks and I don't know what kind of springs. Ride is pretty stiff, but quite fun for me. Boost is about 11.5psi and 2.5" exhaust from pre-cat back with a Dynomax muffler that I think sounds Great with the exception of the exhaust leak from the flex coupler.