Thanks for the input. I am purchasing an edge evolution programmer/scanner this weekend to properly diagnose this and I will update you with the correct information. Thanks again!
"Hissing" in the exhaust system is caused by a closed or partially-closed exhaust back pressure valve (EPBV). Perfectly normal until the engine oil gets up to around 168° F.
Read my posts in the following links for more detail:
http://www.thedieselstop.com/forums/f24/q-high-exh-temps-220961/
http://www.thedieselstop.com/forums/f24/help-truck-sounds-like-jet-taking-off-218962/