all you need is 2 1/4 running 2.5 or 3 is good if your running turbo or anything with boost if you put that on a all motor u will loose to much back pressure and u will loose horsepower and torque

 

This is correct. 2.25 for stock to moderate bolt ons. 2.5" for full bolt ons. 3" for turbo sc. If to much flow will loose low end torque and will kill gas mileage. Exception is if you kill flow at the end, such as 2.5" then imco which will not effect gas mileage due to constriction of turbo style muffler. With glass pack you definately want 2.25"unless header, intake(non cgs), tune, 2.4 intake manifold and down pipe. Hoping you are keeping stock resonator, will sound like a ricer without.