don't expect a miracle out of your exhaust, unless you get catback which might get you 4-5 hp. The best upgrade is a "Cold Air" intake system, I have 4-2-1 headers, aem cold air, 2 1/4 in exhaust catback and I would tell you that exhaust is the least bang for the buck power you will get. Why don't you go with CAMshafts instead for a few hundreds more. Skunk2 or Crower's