Originally Posted by BRMike
A cat back system will yield a few more horsepower, but in my opinion not enough to justify spending $700 to $1,000 (depending on brand). I like the way my car sounds with the factory cat back so I don't have plan to replace it. I would suggest using the money saved from the cat back and put it into some other upgrade such as a shifter (for the M6) or some suspension upgrades. I believe you are aware of the Louisiana Herd crawfish boil... A few of us (five or six) are meeting up at my house to caravan to Covington for the event.
Mike this is basically true however I just read in popular mechanics about a str-8 magnum(i think it was a magnum anyways) .They tested the car then put the new catback system from corsa on it .They dynoed a 5hp increase however there was 20ft lbs of torque added through almost the entire rpm range. 20 ft lbs youd feel.