[Aaron71]

Hopefully this will give you a little something. I Own a 2004.5 LLY GMC with a 118,000 miles on it. These are the modifications I've done AFE Stage II Pro-Gard 7 cold air intake, Silverline T-304 exhaust single 4" with 5" tip Turbo back, Dr. Performance Nitro Flash tuner 80hp/200ft lbs, BD exhaust Manifold, Amsoil 15-40 full synthetic, and Autometer Elite series Pyro and Boost gauge. Here are some comparison to check for yourself. I was about 11,500 to 12,000 lbs with camper and boat on my truck weekend after Labor Day 2006. We were traveling 72 in overdrive up a 5-6% grade with the air temperature 81. The pryo was 1125-1150, Transmission 190, Engine 210 for 5-7 miles. These temperatures with the cat in place. It dropped another 75-100 with the Cat out up that same grade.

 

[Aaron71]

Something else to think about also these EGT temps on my 2004.5 are right in the Exhaust manifold not after the turbo on the downpipe. The techs I've talked to say there can be about 200-250 temperature decrease after the turbo port. I never had to add either a fingerstick or a blocker plate my truck to not code a air flow problem after taking the cat out. The exhaust manufacturer along with other techs claim that only about 10-30 of the LLY diesels would since the cat out. Or perhaps it was addition of the BD exhaust manifold the hp addition of the flashtuner that still make enough back pressure to not set a DTC code.