1995 Plymouth Voyager stalls in gear

1995 Plymouth Voyager mileage: 65,000. I've been working on this van for about 4 days now and can't find any cause for this problem. If you put it in gear (drive) and accelerate, it will start to stall. It has new fuel pump, fuel filter, Hall effect switch, ignition wires, plugs, cap & rotor. Scanned engine for codes and nothing. Thought I had it fixed but the customer takes the vehicle, gets 1.5 miles and it stalls. Same if I drive it. Also when it stalls it will start right back up. I’m exhausted with this van. I've been through all-different types of diagnoses, had 4 other techs give me advice and help me figure out what is going on. Please if you have any ideas, heard of this before, please let me know. Thank you