Yes, a full tune up was done a couple of weeks ago.Problem persists. It still had all the original parts installed at 101,000 miles! As far as a vacuum leak, I don't know. How would you test it? Smoke tester or just look for cracks and low vacuum on a vacuum gauge?

 

A year later.

Put a vacuum gauge on it, see what it does. At idle, you should have a steady needle, at 17 pounds or better. (or less? Whatever, a number 17 or higher. )