350 stalling

I have an 89 RS the engine has been swapped for a 350. Problem is under braking and hard turns, engine all but stalls. its set up with serpentine system from a 4.3, but the belt is new and doesn't feel too tight. Please help this is really getting on my nerves.

your car wouldn't happen to be an automatic would it? It sounds like the converter if it is.

whats your gas level at????? even at a quarter tank, hard braking and hard right turns can starve the pump and the engine will stall. but yeah could be a converter, could also be a leaking brake assist cylender if it leaks vacume with the brakes on, then you will get a stumble and rough idle, in severe instances, it could stall the engine.

Gas level is not a factor, does it full or empty. It IS however, an automatic, hoping that's the problem, it's time for a manual anyway. Thanks a lot guys!