Better handling?

[iceracerdude]

^wow. Why didn't you tell him about the eBay chip. ???
Some people just don't know ... J/k

Ha, ha, ha

[Damkid]

I've moved this thread to the suspension forum where it belongs

[Advancedynamix]

For dirt you dont want a lot of front bar (just like in ice racing). I'd keep the front as loose as you can stand without rolling the car (probably just some stock strings on KYB gr2s), but stiffer in the back for sure. Go with an aspire rear beam (I doubt your tech guys will know the difference) and some stiffer springs (some people have mentioned that CRX or Del sol springs fit and are stiffer) again, doubt you'll fail tech if they are oem springs. Don't bother with big brakes because you won't need them in short track, just the best pad compound you can find. Paint everything that you put on the suspension satin black and get it dusty before you get the car teched. Unless you are dominating consistently, you shouldn't have problems.
For power? well that depends on what you can get away with, what you have for tools and what you have available to you and how much time you want to put into your car. You could probably pull off a B8 without throwing red flags, unless you have a lot of Mazda Guru's that you race against. B6 would be good too, and can be made almost impossible to detect. If your going to run the stock engine, or even a b6 or b8, have the head shaved. Build your engines loose and who cares if it uses oil, its a race car.
K&N or other gauze style filters are essential, and keep them a little dusty. They flow their best when they are a little soiled. They catch the dirt far better than a paper element. Many professional offroad teams (I tested several engines for Robbie Gordon's offroad trucks) actually talc their freshly oiled filters with baby powder to increase flow and stop the heavy chunks of dirt from sticking (it flowed better than a filter sock or skin).

Good luck and have fun!