Right I think its all sorted!

Found the Amal valve plug wires were exposed and looked like they had been shorting out on each other which of course would close the valve and my boost would instantly drop to about 9/10psi (what it boosts to if I unplug the Amal).
Also i noticed plug lead No. 3 was arcing to the head!! So changed that too.

This was all after my clutch cable snapped this morning and i had to get towed home crushing my slam panel and tearing my inner wing in the process because i had the rope around the slam panel as I cant get to my towing eye behind my bumper!!
Thankfully none of that can be seen from outside the car but i will have to get the wing welded and then a quick blow over, which is a twat cos i only got it resprayed 2 months ago!!!