get some high temp 1200 degree ceramic paint and paint all of your exhaust and intake parts. If you can find some 2000 degree stuff, put that on the outside and inside of your exhaust manifold and on the outside of your cat. Try getting the VHT brand. Do many coats inside and outside, about 8 coats will do fine. This should help with some extra hp by keeping the intake temps lower, under hood temperatures lower, and the exhaust velocity higher!
May take some time (let the paint fully cure before running the car! and keep it ventilated so the engine doesn't suck in spray paint!), but I think it works, $4 a can - cheap ceramic coating
Another thing you can do is get a Dynomax Ultra-Flow Welded muffler at summit racing. There only $59.99 and the 2" version flows up to 540cfm! They sound great and a lot better than flowmaster, borla, pacesetter, and those other brands. Check out my website if you'd like some sound clips...
http://1minute.com/dan/