Unfortunately for the moment at least, those replies have been "lost." We've recently performed a forum upgrade, and most (all?) of the old data has yet to be restored.
I'll do what I can to provide a new set of answers for you. I've only encountered this once myself, on my old '97. In that case, the cable that operates the IMRC on one side, actually broke.
Sticking IMRCs are a somewhat common problem. Some have had success freeing them up with repeated seafoam treatments.
I do know that the '96 was a one-year-only, vacuum operated solution. Although I've never taken apart the controller, if you do have vacuum at the device, the next thing I would be tempted to try is to "exercise" the IMRCs manually. They'll be super hard to reach, but I suspect you should be able to get a hand on one with a few contortions.
Hopefully a few others will chime in with "hands on" experiences for you..