Originally Posted by treeman

UPDATE......

I tried bypassing the vacuum reservoir again and car started fine this time - but ran poorly.

I swapped out the degraded section of vacuum pipe - car ran sweet for a few miles and I thought i'd cured it but then it reverted to lacking revs again.

I popped in to my local mechanic, he read the codes and said it's probably the MAF sensor. I told him I'd disconnected the sensor and no difference, and that I'd cleaned it but no difference - he still thought it was likely to be MAF sensor.

Took it into another mechanic, he said it's gone in to "limp" mode, but surely not that as sometimes it revs very well.

On friends recommendation I have taken it to a BMW indy who thought just on my description it would be a fuel flow issue. He has just called to say it was the middle of the 3 fuel pumps failing. Although I'm sure I could have swapped this over myself the indy said he was 100% sure it was that and as the covers where of it would be a very quick job for him to swap it there and then so he has apparently fixed it. Just on my way over there to pick it up - fingers crossed and hope the bill doesn't hurt me too much.