05 Montana SV6 3.5 LITRE HARD START WHEN WARM

05 Montana SV6, 180,000 K.M., new plugs, wires air filter starts and runs perfectly when cold and heater, headlights, A/C on or off. After the engine is warm, the van will not start unless the gas pedal is depressed at which point also runs perfectly!!! No codes at all, no check engine light either. Im stumped?? Any ideas??