I have a 2013 power stroke. If I wanted cat back aftermarket exhaust would I have to do a def delete? I'm just looking that deep diesel sound. Looks like the exhaust filter and the muffler are one unit.

There is a small muffler (more of a resonator) in front of the DEF. If you wanted an aftermarket exhaust you can do from downpipe back or from DEF back. If you go from downpipe back, I would delete the DEF. If you go from the DEF back it is mainly for appearance, small amount of sound. No performance gains on DEF back.

Go with a 5 inch exhaust. It sounds a little deeper and better then a 4 inch in my opinion. Plus on all these new diesels they are all choked down with all the emission junk. The stock exhaust on all of the new diesels chokes them down. Get rid of the stock exhaust and it will help your truck a little bit. I have a 2002 f250 7.3 with a 4 inch exhaust and it sounds damn good but if it had a 5 inch it would sound a bit better to me.

Bypass the DPF and unplug the EGR pump valve. It will require a pro to tune it. Don't touch the pipe. That tips off the man. It sounds great that way.