I have my truck in right now having the tranny rebuilt and I got to thinking with the tranny out it would be a pretty good time to put a downpipe on. I was wondering how hard is this? Is there any particular kind that works well and fits nice? I was told by someone that you need porta power to mash the firewall in is this true? I know a guy at a local muffler shop that says a 3" does not flow anymore exhaust than the stock piece does, is this true? Thanks for any responces.