LQ9 Swap Need Help

[ThumpinCR]

Hi all, looking for some help with my LQ9 swap into my K10. I have been trouble shooting for several days and I am out of ideas. When I attempt start up, it will start up then shut off immediately, every time. I can get it to stay started by pushing on the accelerator pedal and can keep it started by feathering the pedal, however it back fires and does not run good. I sent the PCM to a reputable tuner to have VATS deleted and start up tune put on. I have HPTuners but wasn't confident enough to tune myself.

What I have done. My initial thinking it had to be VATS were not deleted. So I used HPTuners to confirm they were deleted. I used a BP Automotive Harness on the swap. I hooked the power wire to the truck's HEI wire(pink off bulkhead) and confirmed voltage in both cranking and run. Confirmed 12v at the coils during cranking and run. I verified fuel rail pressure with a gauge, 58-60 psi. BP Harness has 2 grounds that I have checked, rechecked and rechecked again. Both are on driver side head. Checked injector pulsing with NOID light. Checked voltage and ground at injectors. I have checked and rechecked every connection. Tried starting with MAF and O2 sensors disconnected with no change. Verified rear O2 sensors disabled. I am getting what seems to be accurate RPMs on VCM scanner. Not getting any error codes on the PCM.

Info on the motor. I bought a 2003 Cadillac Escalade with 200k miles on it. Drove it home approx 60 miles. Ran really well. Then pulled the motor. 6.0 LQ9, DBW. Put a BTR stage 2 cam with new valve springs. Replaced all gaskets. New oil pump. Never pulled the heads. New Spark plugs and wires. Long tube Schoenfeld Headers. 2.5" full length, dual exhaust.

Any idea what to check next? What should I look for on VCM Scanner? This is my first ls swap and all seemed to be going well up to this point. Now I'm lost.

Any advise would be greatly appreciated!! Thanks in advance.