Not sure I understand when the ISV operates in that case.

Never had to use any throttle when starting, hot or cold.

 

It seems as though Porsche designed the system to approximate working correctly if the ISV fails but of course there is no dynamic correction if for instance you change the load by starting the a/c. Thus if the ISV is not working and you have an idle at around 700 rpm, switch on the a/c and you will see the rpm's drop to say 600 rpm or whatever. When the ISV is operational this does not happen and the idle should be a constant 675 rpm with no appreciable hunting.

If the ISV is not working correctly and for instance the shuttle is sticking a bit, the controller will apply more "open" signal until it suddenly jumps to satisfy the demand- this is most likely what happens when the system is surging as mine currently does with the rpms cycling in the range of 650 to 700 rpm. It is not a critical fault but things like that surely do annoy me.

 

Both Delighted and Annoyed - the engine now works perfectly at low/no throttle, I genuinely cannot remember the last time it did, if ever (in fifteen years).

I can now let the car pull in first on a level road with no throttle, previously I could only do that on an incline otherwise the kangarooing would be unbearable.

I had assumed that was due to lash in my 230k mile drivetrain, but no - it was most likely a faulty TPS.