How's your idle speed?  See here for the procedure to adjust it:

http://www.dodgeram.org/tech/dsl/adjustments/2nd_Gen-Idle.htm

is there a vacuum on the air filter indicator?

Just curious but have you had the fuel tank checked for water? It can cause
some strange happenings. A number of years back my '92 diesel started acting
up. It would start fine and run fine at street or highway speeds but the second
I took my foot off the throttle the engine died. It would always start up
immediately but I had to keep the rpm up when coming to stop signs or lights.
Took it to the local dealer and they found over a quart of water in the fuel
tank. Since I hadn't done anything since feuling up the truck, I knew which gas
station it was but never bothered taking them to small claims court over it. It
ended up costing me about $500 to get the injector pump cleaned out, remove the
tank, replace filters etc.etc but it has ran perfect since - and I've never
been back to that gas station !!

cheers,