One more thing...
Check the throttle body air-bypass screw. It allows a metered amount of air to get past the butterfly when you've allowed it to close completely with idle throttle. The idle speed control valve is involved here aswell if it has one fitted and it should be thoroughly cleaned and checked for freedom of movement. No sticky valves allowed! It could cause the fuelling to be adversely affected and screw up the throttle response, perhaps even making it stall on its own from time to time.
Hope it helps