Yep, faulty switch seems likely.
The function of the switch is to tell the ECU to up the power a bit when you are actually turning the steering, so disconnecting it wouldn't affect idling until you turned the steering. It might then stall.
It would seem unlikely that it has anything to do with your erratic idle problem.
Chris
Yeah I've done a little reading on it today, just disconnected it again and when stationary and turning the wheel its fighting not to stall sometimes does. I think your right I doubt it causing the problem but as its at fault I'll replace it.
I guess next step is throttle body and gasket and alignment. Very tempted to use a used on from ebay or scrap yard but could be a mine field. You can visually see a fault with these so maybe worth a new unit from euro or gsf. The little rubber band gasket is £10.91 from vw shocking, and the pas switch sensor £30.53 and comes with a sealing washer. I just have this gut feeling its the throttle body. But have nothing to back it up. I've ruled out vac leak and I made a home made smoke tester with a can, piping very blue peter you can tell I earned my badge no smoked seeped out sadly. Although a neighbour asked what it was explained and asked to test his pug for one as he had a problem and smoke seeped out of a tiny hole on a vac pipe so not a total waste of time lol.