I tried to get caught up here since my last post on it. I know we've been going on and on about vacuum leaks. Have you tried spraying carb cleaner anywhere a vacuum leak could occur while the engine is running. If there is a leak the engine will rev when you spray. I'm sure you've done this, I just couldn't find where. Spray around the intake manifold, base of the carb, all vacuum lines. If you have power brakes, spray that line, same for the transmission line if it's an automatic. Is it possible there is an issue with the vacuum modulator in the trans itself (if auto)? Disconnect the vacuum line to the trans and block it off, see if that resolves the issue.