with your car running right you should have no problem. i was looking at a wrx the other day at the subaru delaership (not really intrested, but it sounded fun) the sales guy talked about those cars like they were worth their weight in gold. he gave them far more credit than an sti. i don't think they would be that big of a deal honestly, the wrx i drove that was only slightly on the quick side had this guy raving about its power, and a stock gn would have walked all over the wrx. i would be prepared to play a little catch up if the guy can drive it, but they are touchy i couldnt' get that car to come out of the hole for nothing, it would either bog down or just not come to life, i guess they have a very small happy place.
if you have any doubts throw a few gallons of 110 in the tank and it should be a pretty easy win.