92 Dodge Caravan jerks and stalls When warm

I am having a problem with our 92 Caravan stalling, and jerking while driving. It has 136,000 miles a 3.0L engine. I have recently replaced all plugs, wires, distributor cap and rotor, fuel filter. The strange thing is that it tends to have more problems when turning right than turning left. Many times just turning into a parking space will cause it to stall. However, when the vehicle is cold it does not have any problems. Sometimes it takes driving for about 10 miles before it acts up and other times driving 5 miles stopping the Caravan at a store when you start it back up it has trouble.
I have had it at the shop twice and he can't find anything wrong as it won't act up when he can put diagnostic equipment on the vehicle.