OOPS! I missed that little tidbit of info! He could try disconnecting and plugging the vacuum line and do a test drive to see if the miss/stumble goes away. That would eliminate movement of the breaker plate. Checking for wobble in the shaft and rotor would still apply.
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!