Ok so i have a 2003 sti type uk and i have had the rcm 3" exhaust with a 100 cell cat and induction kit and had it re-maped at powerstation and it is producing about 323 bhp and 290 lbf.ft. it also has the type 25 handling pack fitted
what would be the cheapest power upgrade be as I am after beating a my friends evo6 next time I'm on the track