Yes, it is stronger than an OS 46FX. One was designed as a sport engine, the other competition. That said, compare the port timings and I think you will find the timings used in the YS are more in-line with those of high performance piped engine. They run fine without a pipe, but won't show their full potential in that configuration. You might try a hotter plug to get more on the muffler, but I seriously doubt it's going to be a big difference over what you see now.

John