So far my f4.6 has been great and my one way hasnt slipped yet. Lots of power. Enty of power actually. I dont think the x needs more really but its never enough power lol. Priming the engine too much is also a bad way to ruin the one wayz. I just do the block exhaust and watch fuel go to the carb way and it works best for me. I see alot of people blow into the line and that seems to make the one way slip more i think. I used to use that method for my revos and i always wet through one ways. Just my 2 cents