2015 gm lv3 4.3 runs rich with maf sensor plugged in, high fuel rail pressure

need help: i have a 2015 lv3 4.3 that came out of a 2015 1500 truck, factory ecm present but has had the program calibrations reflashed to remove and disable active fuel managment operation, vats ect. current is installed in a rock crawler chassie, my question is , with the maf sensor plugged in the engine starts , fuel rail pressure is 650 ish and after a moment fuel rail pressure goes above 1600 to 2000 psi fuel trims ltft's go to the far negative vehicle starts loading up to the point of fouling spark plugs, only dtcs im getting at times are p0101 maf performance, when i unplug the maf the engine dies as i would expect and with maf sensor unplugged when i start the vehicle again frp pressure is as i would expect at around 650 ish and ltft and stft are right around plus or minus 5% so corrcted they are close to 0, the engine will run fine this way if i leave the maf unplugged, if while running i can plug the maf back in and the engine will continue to run ok until i shut it off and restart then im back to high fuel trims all over again, i have worked over the phone with the tuner and they are unsure of the problem we have tried a second ecm with a mirror tune and tried a second factory maf sensor and no luck so im reaching out to the pros on here hopefully can point me in another direction, and advised me on what calibration point i should try to focus my attention on or if anyone on here has had a similar case thanks in advance wayne