I just tried the Lubro Diesel Purge treatment (including fuel filter replacements). I'd like to report that is made a big difference, but that would be a lie. It may have helped smooth things out somewhat, but that's a subjective observation from the guy that just spent $50+ for the pro kit. However, I've got to commend Diesel Giant for their excellent web site. It's a treasure trove of DIY information.

I've ruled out the accelerator pedal and cable. If I pull the "pedal cable" while watching the linkage under the hood, I can see the linkage move slowly back into place after I've quickly put the "pedal cable" back to it's proper position.

Now I know the problem is definitely under the hood. Maybe tomorrow I'll get a chance to pull the intake manifold to get to the linkage.