As far as exhausts go,I have the BullyDog cat-back on my 05'ext.cab. I spoke with many people and decided on the cat back to avoid engine codes for EGR. There are many ways around it but, the full exhaust didn't seem to offer any advantages over the cat-back other than noise. The cat on these things are wide open. If I were to make any recommendations I would suggest the Banks cat-back. It comes the the 4-bolt flange and fits flawlessly. Banks was a big factor when it came to my decision between full and cat-back systems. Being that they have made diesel performance parts for some time and they only offer the cat-back. Hope this helps.