CM870 Turbo Issue

[berrytrucking94]

Hey guys I hav an 06 six cm870 motor, tuned well by a member here. tried searching threads but couldn’t find any with the exact symptoms I’m having but I’m sure I missed a few

turbo acting very temperamental, mostly happens when under load. I’ll be pulling a hill for example and downshift but as I go to give it throttle it’ll spool normally for a few seconds and then sound like it’s spooling half assed and the egt will spike high very fast 1000-1100° within a few seconds.. Excess black smoke, loss of power. If I take it out of gear and let all boost drop then get it back into gear it’ll act normal for a short while until the next pull. Also does this if I hit the engine brake and ease back into the throttle..turbo just sounds wrong

Checked for boost leaks, truck still pushes 38-39psi no problem. Did actuator test and turbo speed test on insite multiple times and both passed. No leaks from air control valve, no oil in turbo and hardly any play in the wheel. No codes either

Any ideas/ suggestions are appreciated!