If you haven't cut the pinched off of the tips of the Bisson pipes already, do so. That will perk things up a bit. The numbers you provide with the 22-10 are really low. The MSC is pretty close to what you should see, perhaps 100-200 rpm low.

Overall, the numbers given make it sound like the engine may be on either side of the correct mixture settings. It's definately not whre they should be. Then again, I don't have a clue to your altitude above sea level.

Question, is there a possibility that the Menz 22-10 is actually the one with the higher rpm?