High Idle problem, any suggestions please?

[Sam3R]

Evening,
I started my 3R this evening after a run out and I think there was a pop/crack noise when it fired up.
It is now idling at a little over 2000 rpm. When I put my foot on the accelerator, the fist centimetre or so of travel drops the revs off and then it revs as normal under drive (still staying over 2k rpm).
I've check the pedal and the throttle return and both seem to be working fine.
It didn't seem to be pulling quite as well on the drive home, maybe about 20% down on power but the engine sounded smooth and normal so I don't know if it's a spark plug. Do they run better than you'd expect compared to other cars with a cylinder out?! Could a spark plug going explain the high idle?
Any help/suggestions appreciated.
Thanks
Sam

[steveobes]

idle valve sticking.
intake manifold leaking, take off check gasket.
check butterfly valve is closing properly at idle.

[YellowShed]

Air leak. Check the rubber vacuum take-off on the inlet manifold under the throttle - probably popped off and sucking in air.

YellowShed

[Sam3R]

Cheers for your help guys.
Your suggestions and a photo from Dave at Jetstream showing me where to look (clearly I have lots to learn) helped me locate this little fella.
I may head to Ace Cafe tomorrow eve if anyone is about.
Sam