Car: 55 plate Mondeo, 1.8 Duratec petrol engine.
After pulling to a stop and disengaging the clutch the revs sit at 2k for around 2 seconds, then drop to around 1.5k for another couple of seconds before dropping to normal approx 900.
If I rev the engine when stationary (say to 3k rpm) then when releasing the accelerator the revs drop to around 1.5k for a couple of seconds before dropping to normal.
This has suddenly started happening and there are no other symptoms like rough running, rough or hunting idling, or hesitation under acceleration.
I'm thinking either a leak in a vacuum pipe, or MAF sensor. I've only got a short time over the weekend to look at it so any further suggestions would be welcome.