If you are doing rally-cross, leave your car stock for now. Gut it, rip out anything unnecessary like the stereo and air-conditioning, and put a proper seat/cage in it.
Leave the engine bay stock. You are on dirt, not tarmac, rallycross isnt about power, its about finesse.
Also, just as a FYI, the SVT suspension (which is what you have on your car) is NOT, and i repeat NOT good offroad. there is a reason that the rally cars all have huge suspension travel and soft shocks. You want the tires to stay in contact with the ground, not skitter over the tops of the bumps.
I have taken my SVT on a windy dirt road with the stock SVT suspension, i honestly did better in a stock ford escort because it didnt wash out like my SVT did.