Takes a lot for me to get stumped but I'm getting there quickly on this one. Vehicle is an 07 Avalanche with an LQ4 swap, 227/234 111lsa camshaft, shorty headers, the rest is pretty much stock. Has GM Truck 36lb Flex Fuel injectors in it. The truck runs perfect, idles great but has a part throttle medium load pop through the exhaust that will not go away. Happens around 20% throttle area at 2500-3300rpm, start popping out the exhaust, give it more throttle goes away. The only way I've been able to get rid of it is to bring PE in WAY early like 12-14% throttle area, which in the past 10+ years of tuning vehicles I've never had to do. If its in closed loop and running 14.5~ AFR it will pop, if I fatten it up in PE or take it out of CL and command 13.5 or less the pop will clear up. Ive moved timing around in the area from 15 to 27* nothing changes it. Tried running SD with the VVE only, still does it. Tried running full MAF mode with the high speed air calc pid set to 1000rpm, still happens. Happens around 75-85kpa of MAP. Seemed mechanical to me so we swapped injectors, coil, plugs, wires, no change. Pulled the truck intake off to make sure no one rolled a gasket, re gasketed it no change. Did a compression test and leak down, all looks ok.

As a test I temporarily turned misfire detection back on above 2000 rpm and the PCM did show misfire on cyl 3 when the issue is happening.

The customer is insisting its the tune but I just don't see it but I'm not completely closing my mind to anything at this point.

Would love if anyone has any input or any suggestions, I have the customers vehicle here now so I can go data log and post if need be.

Tune file is attached.BLT_2109_1_0004.ctz

Thanks in advance!