I wish there were more mods for these engines. If I go 1 step larger with 4 strokes above my hs144-f I will be tossed into the modified class with much stronger engines. So if I want to stay in my class I have to find what mods I can to bump my current engine up, what little I can. I added maybe 25% more rpm and made it breath much better, enough that I needed to drill out the main jet 3 sizes. Since I got my new sbp air filter, think I can step is up 1 more size. My poor mpg has gone from around 115 mpg to maybe 80 mpg if I am nice, but that's rare. I normally get around 65 mpg, my right hand can't help itself.... it has it's own mind.