man I was just throwing some ideas out there.... I'm working on about 2 1/2 hrs sleep. That must be an early LS1 motor I think those had that x-over tube... not really sure. I'd still double check those O2 sensors you got to make sure they aren't bad. Also did the exhaust shop put the new bungs in about the same place as the old ones??

Maybe someone else will chime in here... I need to get some sleep.