I am thinking about upgrading the exhaust in ’05 CC/SB. If I am not mistaken, the stock exhaust is 3.5”, correct? Is there going to be a big difference in the 4”? Only a ½” diameter difference. So should I go with a 5”? Will there be a noticeable difference between the 4” and 5”?

I am going to delete the cat either way I go for the increased responsiveness. Is there anyway to keep it from throwing codes without the finger stick and EGR blocker? Maybe EFI live (would like to get it anyway).

Thanks guys,

Steve

Unless you plan on running 500 HP or more ( I believe thats rear wheel power) Then go 5". If not then 4" will be enough.

Go EFI live, then you can program your truck. Even better, it comes with 2 licenses, so you can get a buddy to half it with you and its cheaper than most tuners. But it will do much more for you.

Neither one matters because the "V" band clamp area that ties the lower exhaust to the turbo down pipe ID is only 2.890". This is one area of distress for sure. Everthing must bottle neck through it to get out.

bump

the biggest benefit of the 4 inch is mandrel bends. same with 5. id go 4

5" is overkill IMO, but does look cool. 4" is all you will need. If you want to stay clear of the code issues, stick with cat-back.

I am thinking of geting EFI Live as well, wont this resolve the code issues?

5 is alot deeper sound

I really like the sound of the 5" over the 4". Glad I bought it!