I got a stock dp what would a 4 inch do for me if i wanted too put one on

 

it frees up backed up exhaust better flo more power but not much and it lowers egt i got a 4 in dp to 5 out i paid 300 for the whole set up

 

Yes run 4"from the turbo to the muffler get rid of the resonator/catalitic converter whatever it is not sure,or straight pipe it too! Also remove stock air box put on a big k&n or a bhaf or something,Did notice a throttle responce improvment on mine

 

I wouldn't just replace the DP by itself. I would do a complete turbo back exhaust.

Luke