Have this nice old truck and the idle is really inconsistent.  It will
bog, then over-rev trying to recover then hold idle for a few.  And then
repeat again...  Happens more when engaged in D, especially at a stop
sign or light.  I have sprayed around the intake gasket with carb
cleaner and no change.  Injectors have been pulled and cleaned
(supposedly) along with a full tune-up...  New Oxygen sensor...  The
tuneup was farmed out to a mechanic who came recommended as I needed
some seals replaced along with brakes.

Any ideas of where next to look?  

Thanks

Carl