GTI Idle problem

My Golf GTI 8 valve will not idle properly when hot. It consistently revs at 2000rpm or more and will then 'hunt' from 1000 to 2500 rpm (up then down) in a regular, quick cycle. Switching the engine off, then on again will sort it out for a short while, after which it will starting hunting again. When cold, the engine idles beautifully.

Can anyone help?

Sounds like the Cold temp sensor... The blue one on the block water outlet, usually the one closest to the block... Replace that, and it should be fine... I had the same problem in my old Jetta MKII, and it fixed it... Also check that grounds are on all the way around, and make new one from the block to the chasis and from the Bat neg the the cahsis, and to the block.. MAF might be the culprit too, it's the little box on the air filter box...have fun, and remember, VW's are good cars, just pickey...

what about idle speed sensor on the TB.

I would check the knock sensor that mounts to the front of the block. Mine had the same problem. The knock sensor computer only kicks in after your engine heats up to normal temp. I got the new part for about $60