Fwiw, the Webra is basically in the same boat. With a mousse can, it really is more powerful than an OS .25FX, no question about it. The huge carb opening is a big reason why. The Webra also has more aggressive port timing. You can actually add quite a bit of power to an OS .25 just by putting an OS .32 size carb on one. Instant power increase.

The downside of the large carbs is that fuel draw is reduced, so you have to be more picky about your tank install or use a bladder or other fueling system. I don't have any problems with my Webra's on a normal tank, but I know other guys have, and I think that's a big part of why.

On muffler, the Webra seems to be a bit more powerful. I'm using an OS muffler on my Webra's, with the baffle removed. Same muffler on the OS engines, and the Webras seem to generally out turn my OSes. YMMV