116000 kilometers 1988 Dodge B250 conversion rv van has a miss and mechanic cannot figure this out. I have had fuel filter, fuel pump and sock, spark plugs, wires, distributor cap and rotor, coil and magnetic pickup in distributor changed and mechanic said good spark and fuel injectors or good. Mechanics took for ride but only happens when i go on a trip and after driving for awhile and more noticeable on hills and when gas given van shakes until i let off of gas pedal. No engine codes. Another problem that just happened is when i put defrost on no fan speeds are defrost but works on vents ok. Is there vacuum lines are actuators or both and where are they. thanks Mike