Hey i have an 03 regular cab with the 5.3 and am about to buy headers, Pacesetter to be exact. Anyways my question is a) what size pipe is it from the manifolds to the muffler and b) how hard would it be to modify a stock y to longtubes?

 

longtube headers and stock y pipe wont happen
spend 120 and buy the pacesetter 3 inch y pipe that bolts to the stock exhaust flange in front of the muffler

 

I wanna keep my cats because of inspection issues

 

buy high flow cats and have them put in the pacesetter y pipe