Like gtpinsc said, Gm and their wonderful location for the o2 sensor. Go to a good exhaust shop, tell them you want the u-bend in the exhaust taken out and a straight piece put in place. They will match the correct size pipe to weld in place. You cant miss it when you look under the car. This will get you around 5hp and the car will breath better! Shouldn't cost more than $25 30 bucks.