Mine has been unhooked for quite a while because the intake temp switch for it went out. No issues here. Mine is a 92 so if the ksb is unhooked, it leaves the timing alone. I believe on the older models (pre 91.5), no power to the ksb will make it stay advanced.

 

I hooked 12v to my ksb while the engine was running and it made the idle drop some and made it really rattle under load.
I'd say like was posted, sounds like an injector but you might want to pull the oil filler tube off the front cover and make sure the pump timing gear has'nt slipped or somthing.
My truck had a similar episode with heavy smoke on 2 seperate occasions. The first time it was a sticky injector, 2nd time was the pump timing gear had slipped.