Ford Repair: 1989 Ford E-350, engine gasket, shuttle type

Question
I recently bought this unit. It is a shuttle type bus. Has 22,000 actual miles. Bus has a 460 fuel injected engine. Runs great on highway, Idles slow and very rich. Exhaust smell is very strong. After long idle, it gives off a white gray smoke which will go away with a mile or so of driving. Only had a couple of gallons of old fuel in it and I filled it with 30+ gallons of new fuel.
Unit has sat a lot  Any input would be greatly appreciated.

Answer
Joe, the white smoke usually indicate that coolent is leaking into the engine.  Which means an engine gasket changes (i.e. major engine repair).  However, before we go that far, look into changing the engine idealer control unit.  Not sure of the exact location, then do the usual, fuel injector cleaner, filters changes... and see what happens.  If the white smoke still presist, then look into the foremer issue.  Thanks!