And I didn't, both P1351 and surge came back

 

did I recommend checking the torque on the intake manifold bolts. im running outa ideas.

 

Hi Craby
Yes you did, in post #17, think I have covered all possible causes for vacuum leaks doing block offs, smoke test, and spraying carb cleaner all over the place

Picked up the PCM yesterday to do a conductivity test on the white cable going to the ICM (the one with the too high voltage causing repeated P1351's after installing new wires and plugs) and found a partly damaged cable under some dried out old tape, a orange cable in the corner of the black connector which seems to be one of the PCM power supply cables, a part of the plastic has been shaved off and the copper inside shows green corrosion.
Gone try and fix it with one of those solder filled crimps

 

Regarding the surge, after cleaning up the Opti connector it got reduced a bit more, its less frequent and less aggressive now at idle (the big change came after replacing ICM and coil as mentioned earlier).

At the beginning of this troubleshooting I replaced both the TPS and IAC, but I choose China cheapos as I wasn't sure if they were bad or not.
The new TPS failed rather early and the car started shift gears very oddly, but after putting the old one back it was ok again. As the IAC is of the same brand, I don't trust that working optimal either.
So I ordered a AC Delco IAC that I'm waiting to arrive now, we'll see if I get lucky.

Btw I mended the broken PCM cable in the previous post

 

kool hopefully it works out for you