This may sound like a stupid question (probably is) but how much more free flowing will the exhaust be by leaving the turbo through a 3 1/2" (or whatever stock is) then flowing through a downpipe that is the same diameter for 2-3 feet before going into the 4" exhaust?

It just seems to me that a 4" turbo-back would be muuuch better! But, then again, I don't know much about how these things work.

I guess the real question is: How much benifit do we really get with a cat-back system? Someone please help me understand :help2: .

By the way I am considering a new exhaust and I would go with the cat-back if it is just as good as the turbo-back in order to make dealer visits less of a hassle.

Just get rid of the damn cat, I seriously doubt you'll regret it. I'm ousting mine as soon as I can afford a full MBRP system.

>>>>off to check on how the money tree is growing>>>>

The Cat does cause some restriction as well, and from what I've been able to find out, that's when you start throwing codes. NOBODY makes an actual Turbo back system, the best they can do is really a downpipe back system. I use to run in the high horsepower Cummins club, I can tell you from first hand experience, the downpipe right out of the turbo makes a BIG difference. If we could somehow push the firewall back or something to allow a bigger turbo downpipe, we would see a very noticable difference. But with any diesel exhaust, the less restriction the better.