Originally Posted by CobaltSSOCZ

I have a hahn catted dp and K&N SRI installed on my car. The only 2 mods I currently have outside of GMS1. Not throwing any codes and the car runs perfectly normal (Except it is very loud on cat warmup now). Fuel trims are a little off, (I'm not getting as good gas mileage as I should); however, we are talking a loss of only 20 miles per tank I think. Not back firing or anything though, and it was driven very hard one day last week when we went to the track. Basic conclusion, it runs fine on both driving hard and very easy; however, I would get it tuned as soon as you can afford to because I'm sure the car wouldn't like it over an extended period of time. I'm hoping to get mine tuned by the end of july.