Engine stall on right turns.

This is the 1 ton 3500, 15 passenger van. HISTORY: Engine recently swapped. Original manifold used to allow new engine to match, used original hang on parts, starts easily, runs smooth. ISSUE: Engine stalls when making right hand turn. Only occurs when traveling above 15 mph. Immediately recovers when steering is straightened, and left off throtle. Dash lights do not falter. The stabilitrak light (lower left dash) and sometimes the check engine will "Flash" when stall occurs. *Failed to start once, seemed to not be getting fuel and did not have pressure on the test valve on the top of the engine. Pushed van to gain access to check fuel pump and the van started.*