I need advise on tuning a PCM.
We have replaced a 400CI with LS6 Heads (550HP / 510 torque) to a 383CI stroked with LS6 Heads. The new engine has lower compression (around 11 or higher) while the old was slightly higher. Same intake, injector, headers. Cam is close to the last Engine.

I read the PCM and Changed the CI parameter and had to perform a full flash because the Grand-Am racing PCM did not have a serial number. We have not proceeded with the crank sensor learning.

Current results: Engine cranks and idles at 1600 RPM although the desired idle is at 1000 RPM. The MAP and MAF values are within allowable range. I believe that the rational test fails which triggers the MAF P code. We do not have O2 sensors installed for sensor 2 and are disabled in PCM but we do have sensor 1 installed for both bank 1 and 2. The values at idle of the O2 sensors seems real low (.0020 mV). The command AFR is set for 13.5. The fuel learning is enabled but are resulting in 0%.

This is a road race car and we are expecting around 510Hp with 475 foot pounds of torque.

Question: Does low mV readings from O2 sensors reflect lean or rich? What is the best plan to start tuning?