Golf MK1 carb problem?Fraustrated

Hi guys, I am new to this site. I have a Porsche 356 replica which is fitted with a Golf engine instead of the usual aircooled item. The problem I have is cutting out when braking/slowing/reversing. Ok under load but dread junctions/traffic lights etc. Have cleaned tank and put magnets in. Sorted out fuel lines that were not A1. Checked fuel pump. Cleaned carb out.Not sure what the carb is but has four long bolts not three.
The idle is erratic when cold but solid when hot until it cuts out and speeds up as engine gets warm. Need to keep revs up at junctions etc. The car is great otherwise but makes me long for a good old flat four air cooled.
I am in Botley near Southampton. Any suggestions appreciated. Might it be sucking air from carb base/gasket.manifold gasket? Would that explain the speeding up of idle when hot? It has been suggested there might be a hole in an idle diaphram? Cannot even work out what this carb is as it does not seem to be the usual Golf type? CAnnot find a four hole carb base plate all seem to be three.
Fraustrated and fed up by the whole thing. YOu might be my last hope.  

Measure the mixture and take it from there.