I own a MECOA .46 Tomcat & the break-in is painfull -- it doesn't run well out of the box. Once you get it run-in, it is OK, but not spectacularly powerfull. Same for the GMS .47 (another bargain price motor) -- long break-in, somewhat fussy & good, but not outstanding power with the standard muffler. I put on a GMS tuned muffler & that woke it up considerably -- equal, or a hair better than my TT .46 Pros & my OS .46 FX with stock mufflers.

The TT Pro & the FX are pretty evenly matched, & with the stock muffler baffle removed they out power the GMS with its tuned muffler. Add a GMS muffler, & they both blow the GMS away.

The MECOA also benefits from the GMS muffler, but it can't match any of the others for power. However, it is tough & long-lasting.

My favorite .46 engine by a wide margine is the TT Pro -- I have 5. I no longer have the GMS or the FX, but I kept the MECOA for "severe duty" applications.