Guess I posted in wrong area, have a 05 common with tripledog, bulldog airbox and filter , and mbrp 4" exhaust from resonator back, didn't start this till after upgrades, new thermostat , fan and clutch ok , cleaned rad,cac, and condenser inside and out! Possibly resonator plugged? Help !! Runs fine without load

 

You did use a Cummins T stat, aftermarket ones are not that good and you used the proper amount of HOAT coolant & distilled water? Are you 100% sure that you got all of the air bubbles out of the cooling system? Also what are your EGT's temps at being I see you have a BD Tripledog?

 

Genuine cummins and yes used airlift to put coolant in, pyro stinger is out don't know egt, may buy new stinger @ work 2morrow