Thanks Grom, your advice and knowledge on that thread was invaluable. Turns out the garage had fed the vac line across the top of the 1" airbox pipe rather than behind it. Once re-reouted and pulled down when lowering the problem wwas solved. So thank you.
Picture on my "Hello from Scotland" thread ont he introductions and new members forum.
https://www.vfrdiscussion.com/index.php?/forums/topic/89439-hello-from-scotland/&tab=comments#comment-1097554