Hmm, this is my third attempt at a reply, the other two did not post for some reason. After hitting 'submit reply' it gave me a message about a moderator needing to approve my post before it showed up, but a day later they still haven't showed up.

I'll try again. It never hurts to offer an idea, but I would prefer to fix the problem correctly. If there comes a moment when we are up against a time constraint, then I will look into that. I have checked the throttle cable slack per Mr. Dalton's suggestion and in the process of doing so, discovered what appears to be a broken throttle return spring. This would most likely set off the same codes as not enough throttle cable slack if the throttle isn't fully closing, since that would cause the throttle closed switch not to activate as well as low manifold vacuum. I am going to switch it out ASAP and will report back.