Replaced SMC - Slow System - No Audio

2017 MBA A1466 (820-00165) Monterey 12.7.6

We thought the issue was a bad SMC, We replaced the SMC, Connected the charger, Brief fan spin, no chime or boot. No water damage, clean board Technician cannot find any shorts. The issue remains even with no KB connected. We have reset & programmed the SMC with SMC tools / Unable to reset PRAM etc...... Only with SHIFT+OPT+Power I got it to boot into the system, fan at normal speeds, power button does shut it down....But the system Prefs wont load and it is dead slow. I have used 2 new keyboards shells and 2 good TP cables yet still the same, and with a fresh Monterey installed drive. Diagnostics no issues found. The KB & TP are functioning fine (Except to power up). In recovery mode the terminal sudo nvram -c command is not found. Firmware password is off. @danj @oldturkey03 What can be our issue here?

System Firmware 489.0.0.0.0 correct for Monterey.

SMC Version 2.27f2

No Audio devices are detected with 2 I/O boards, which maybe our issue? Although it did chime once before.... Charges battery OK .....I eventually have successfully clean installed a copy of Monterey on the unit but everything is still the same.... At least I thought so but it has stuck on 12 minutes remaining for quite some time now, I will have a sleep and see if it finished when I wake up.