Before you do too much engine work, make sure you have matched props. Test multiple props on the same engine and match the two with the closest peak RPM.

If your engine out-of-sync is constant in nature and difficult to remedy, you can actually use mismatched props to correct for this. Again, test multiple props on the same engine, and then use two props with dissimilar peak RPMs and put them on the two engines appropriately.

Regards,
George