Hey, I did rallycross for about 5 years and now I do stage rally. By far the biggest bang for your buck mod is proper tyres. Most rallycross organizers allow snow tyres in the modified 2wd class. I like Bridestone Blizzaks. Just do a tirerack.com search for snow tyres in your size. Next I would remove the front sway bar end links and add a SVT rear sway or larger diameter rear sway bar. This will cut down on understeer on turn-in and allow you to rotate the car easier on the tight rallycross courses. Disconnecting the front sway bar also allows for full droop travel on your inside front tyre during cornering so you can get on the power a little sooner. As for springs the SVT springs would be a good idea or stock ones would be fine. You want as much travel as possible to keep proper contact patches. If you're getting adjustable dampers set them for rather soft compression damping and medium front recoil damping and somewhat stiff rear recoil damping. If you adjust your dampers this way it will also help to rotate the car and you won't need such a drastic sway bar set up. I would recommend a skid plate if you have the facilities to make one. But if there aren't many rocks where you're racing you can get away without one. And if you have the pockets for it, an LSD will shave big chunks off your lap times.
understeering? visit FealSuspension.com
for quality repairs and modifications in the LA area: StevesAutoClinic.com