honestly, the best thing you can do for autocross is practice as a driver, i frequently autoross a c6 vette with lots of engine mods... it puts down about 370 at the wheels but me and my buddy who owns it where over a second apart on our time on a 30 second course (i won btw
) at the anual vette fest, but the bottom line is, autocross is about 75% driver, and about 25% car, i'm not saying you can take the alero against huge horsepower rwd beasts with slicks, but you may be able to take on faster cars if you up your driving. technically though? suspension brakes tires are the best things to modify and if your going turbo, deffinetly an lsd otherwise you won't be able to out your power down