no luck with the iscv then? can't say as i'm surprised. i'm not saying it is defintely a leak, but it sounds like one. but it could also be a sensor fault.

to look for an air leak, get some bradex easy start or other volatile spray. spray it around various joints on the inlet side and if you hear the revs rise, then you know that it has been sucked in, improved the combustion and made the engine run better.

aother way is to pressurise the inlet system and search for it, but that's difficult at home.