no communication 2000 camaro pcm, wiring, 5.7, T56, 1976 280z

[greggbruceauto]

I have searched no communication, detect protocol failed, and a bunch of other stuff in these fourms, but still having no luck.
1976 280z, we have installed a 2000 camaro 5.7, T56 manual trans and harness, along with a brand new DLC connector.
I have checked and rechecked 4 times, the power and grounds at the DLC, also checked continuity to pin 58 (serial data) of the pcm, also checking for short to ground and short to power, but can find nothing abnormal.

None of my 3 scan tools will communicate with pcm, car would start and die in 2 seconds, suspected VATS issue, customer took pcm to a tuning shop and they bench programmed it to ignore VATS and eliminate rear O2 sensors, vehicle will now start and run, but still will not communicate with any scanners nor HP tuner....

Have checked batt power and ign power to pcm, checked pcm grounds, still no communication...

Should there be a resistor or something on the data line?
DLC pin 2 is serial data, 4 and 5 are grounds, 16 is power.
I have wiring diagrams for this pcm and harness, and checked all inputs/outputs for proper location, still no communication

--what am I missing?

[Chrome_Rust]

Shoot me a PM with your number. I will give you a hand. Diag tech by trade.