MG Car Repair: 1973 mgb, manifold vacuum, vacuum advance

Question
My 73 B has a new distributor, timing seems ok, rebuilt carbs, working well enough.The car starts fine usually not needing choke idles good @1000.My problem is when the car warms up it barely idles maybe 400/500rpm and will stall if i don't pump the gas pedal.When running rough last night i pulled the vacuum advance hose off the intake manifold, the idle smoothed out and was running well again around 1000 rpm

Answer
Andre, it sounds like your timing is set wrong (if you do have a vacuum retard unit on the distributor)

Only vacuum retard units are connected to manifold vacuum and the fact that it speeded up to 1000 RPM with the vacuum removed is a conformation that it was a retard unit on the distributor.

All of this indicates the initial timing is set wrong.

Howard