Hi Martin
Thanks for your reply. I did torque to 9nm , but will try again at 8nm=6 lb/ft .
I did tighten the bolts in a sort of alternate opposite sequence, but not as you've mentioned regarding the centre bolt. That may be the cause of the vacuum leak as it may be creating a slight distortion in the manifold / gasket.
I feel that this a simple fix, but for the life of me I cant find it.
I did try the retrain procedure with no joy, but I'll try it again.
Thanks again
Michael