Im getting my car into the shop next week to get a 3'' High Flow Cat from carsound and a flowmaster 80 muffler that is a 3'' single in dual out. Will this help with my gas mileage and performace? I seem to be getting around 10mpg!! Check sig for mods

 

Unless you're cat is bad, it's not going to help much at all, there is something else wrong to cause 10mpg.

 

ya my cat is all F***ed up. it rattles and causes the car to hesitate. When it was at the shop they said it was because the cat and muffler are really bad.