I'd suggest doing a test drive with the vacuum advance disconnected and plugged to see if the exhaust note changes when coasting. Running full manifold vacuum to the advance is generally not an ideal situation unless you do some tinkering with the total travel of the centrifugal advance weights and/or the spring rate as well. Drop me a PM and I'll respond with a phone number. I have a few ideas that might be better addressed in a 2 way conversation instead of with a keyboard.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!