Garth

I had the exact same situation on my MC21 it had MC18 electrics. The reason previous owner replace them because they could not find a replacement PGMIII, so they had to replace the sh*t out other bike, loom, PGMII, alternator, Flywheel. e.t.c to fit a PGMII
in order to connect the PGMIII loom with the MC18 alternator/pickups i had to fabricate an extension on cables because they are too short

I now almost back to stock except the flywheel/pickups/alternator which i still looking for. Now for the effects. I believe that the advance is deferent on MC18 flywheel less advance, One of some problems affecting hard starting as timing is deferent.

Any other effects on power i dont know since is my first MC21 ever.