once van is warm occasionally will miss a little and have slight power loss andengine light will begin flashing. the plugs and wires have been replaced and coils have been replaced. still have condition. where do we go next?

Flashing from your check engine light indeed indicates an engine misfire is active. Due to the intermittent nature, I'd still suggest a concern with the plugs or wires. Ensure spark plugs are not cracked in any way. Focus on the diagnostic trouble code you retrieve for the failed cylinder or cylinders in question. Make sure you are using high quality - GM perhaps - ignition wires.