my friend has an 05 dodge 2500 diesel and he was looking for an exhaust. he saw a 5 inch setup and was wondering if tht would hurt to run it? any help thanks

On a turbo diesel the bigger the better on exhaust size. Chances are though that a 4" would flow as much as he would ever need, but there will be no harm in running an "oversized" exhaust. JMO.

Alot of people that run 5 inch on there cummins end up making it quiter the cummins has alot of cab noise with that big of pip