there right 318's are hard to get performance from take it from me i have a turbo charged ti and i am still looking for more horsepower. I am about to buy an apexi fuel map controller and have it professionally tuned hopefully that will help a lot. For your exhaust, you can spend over a 1,000.00 on a supersprint like me or uuc or whichever one you are looking at, but if you want a better horsepower to money ratio buy a 2 1/2" high flow cat converter, pick out a nice muffler and have your local shop bend you a custom exhaust all costing you about 300.00 and you will get more horsepower from it too. See after market exhaust will still have federal regulatoions like resonators and over sized cat converters which does not gain you any horsepower at all just nice sound. I had a supersprint put on my car and gained 2.3 horsepower, after my turbo install i had a 2 1/2" custom turbo back exhaust made with a high flow cat and a ac autotechnic muffler with 4" removable silencer and gained 9 horsepower all for 325.00 installed.