did you read the previous posts?
your advice is generic and not specific to what has been posted.
Need more info if you're going to replace the PDS bearing(s)!
Post your engine model number.
You may have a single bearing
Do you have pics? I believe they put the phazemaker in the 1971 and up motors that is the red module with the large capacitor on the side. I have a 1969
RING SET #378432/0378432 item #30595779594 On E-bay ony1 day 8 hrs left 20.80 3 rings per set
Backfire is usually caused by a "lean sneeze" (lean fuel condition), or slightly retarded timing. If it's random, I would go over the complete