M42 surging idle is fine when ICV unplugged!

[unixnerd]

My M42 idles roughly and sometimes stalls at idle when warm. Perfect when cold.
If I unplug the ICV the warm idle is perfect at 800rpm! I've cleaned the ICV and it seems fine. I THINK the ICV is open when unplugged, closed under power. So by unplugging it I'm letting in more air (I think!).
TPS gets 3.9kOhm pins 1-3, 1.7->4,4k pins 1.2 depending on throttle position. There is a tiny bit of slack in the throttle cable at idle. I think this is a good test.
I did the "mess under the intake" pipework cleanup a few years ago and deleted the throttle heater so my air piping is newish as are all of the intake gaskets (inc. manifold). Don't think it's a vacuum leak.
Car runs perfectly except for warm idle.
Any thoughts? I'm suspecting the TPS or the wiring to it.

[Dj Buttchug]

I would smoke test your intake system first and see what you find. Also check your throttle body boot for cracks.

[unixnerd]

Wish I had a smoke tester! Can't see anything, will have another look........

[MrBurgundy]

Just spray some brake clean around the intake and hoses and see if your idle speed increases.

[monty23psk]

if you smoke cigars, grab a full bodied one and find one of the hoses at the end to push smoke through. Or you can build a smoke can, with diesel plug, baby oil and a can.