I've flown mine with both the MSC 26-10 and the Mejzlik 27-10. I tached the Mejzlik at 6250 a few months ago.. I don't have a number for the MSC. I have the stock mufflers. I bought it used from a friend and it's had many gallons throught it. It's a good motor if you find a deal on a used one. Not sure if a would buy new as the cost difference vs the 110 or other motors in the class is minimal and the newer and cheaper 80CC stuff is closing the power gap.

I do have a few nits with the 105:
(1) no headers are readily available. You can order the exhaust adapter from BME and make your own.
(2) I've had trouble with prop slippage. You need to tighten it like your trying to break it! I also use sandpaper disks between the components. I'd much prefer the 6 bolt adapter. That would also make prop and spinner fit compatible with my other 100cc class stuff and save some $$$.
(3) It's not cost effective to upgrade to the 110. What you have is what you have.
(4) The customer service isn't as quick as the other distributors. I got my good deal because my friend had sent his motor in and waited along time for the service. He flys IMAC and has switched mfgs to get a quicker turn around if he needs it.

Don't let the nits throw you if you find a good deal. My starts easily and pulled a CompArf 2.6 Extra with no problems. I sold the plane but liked the motor enough I kept it.....now if I can find a prop adapter.