Back in the summer I had problems with the throttle rising and falling at idle as if I was revving the car to 1500rpm and then releasing the throttle constantly. This was caused by an I/C boot not being installed properly after a plug change, which resulted in a boost loss.

The ecu was reset, boot reinstalled properly and the car seemed to drive normally again. However over time I came to realize that when I came off the throttle /changed gear, the revs did not fall as quickly as they once did. I checked out the map sensor a few days back and it was pretty oily so cleaned it up, reinstalled it, reset the ecu (unplugged battery) and went for a drive.

Wow what a difference it made. Car feels much better now with revs falling more readily however im still slightly doubting If the problem has completely gone. In 3rd gear for instance when ive come off the throttle the revs do seem to linger a bit and not fall as quick as I believe they originally did.

Looked at current MPG on the OBC and after lifting off the throttle, the values don’t jump straight to 99.9mpg, it will go to something like 74.5mpg then to 99.9mpg. Is this normal, do other’s cars do this? I realise that’s not the most scientific test there is but when the car had a boost leak and you came off the throttle it would come up with 3 values before arriving at 99.9mpg.

The I/C boots are the originals and am planning to swap over to some new ones soon as it should help create a better seal around the horns and stop any air still escaping.

What else could be causing this? Where else could there be a leak of boost? I had an idea it could be the BPV if the spring resulted in the not shutting off quick enough. Any other ideas or solutions greatly appreciated guys.