right, the mystery gets deeper.
I found that the connector to the vacuum pipe had a twist in it, which presumable meant the vacuum to the VNT valve was insufficient, I disconnected it, removed the twist pushed it back and was feeling confident I had found the problem, the car ran well with lots of power and good low end pick up.
However when I came to start it the next day it would barely tick over, stalled when under load, eventually after a minute or two I was able to get it moving gradually building the revs up. During this time there was a lot of smoke, then after a further minute or so the car flew, but again high smoke and low mpg, around 20mpg.
I have inspected both turbo hoses to ensure I had not disturbed anything, all fine, air filter still clean. I forgot to add I put on a new genuine (from Alfaworkshop not ebay!) MAF a couple of months ago. No MCSF light on the dash. Still getting that blowing out of the air intake box which does smell strongly of diesel fumes which is a puzzle.
Any ideas what is going on?