46AX superceded the 46FX and has been available for about a year. AX is currently available only as the 46.

IME it is as reliable as its predecessor, and marginally more powerful. Only issue I can fault with it is the adjustment of the low speed needle. With prolonged ground idling with that enlargened boost port and typically high contemporary timing, the AX tends to splutter when the throttle is advanced before it picks up, and judiciously conservative rate of advance makes no difference. Adjusting (leaning) the low speed needle to completely eliminate this will result in too lean a bottom end for normal (in flight or non-prolonged) idle operation. The workaround is to set the idle RPM itself higher than I perceive as desirable, which masks the problem and reduces the severity (dead cut) in effect. Though the OS AX carb is superior to the MAG and doesn't present the problem in transition, the symptom is typically Super Tigrerish, arguably unavoidable in accommodating that huge boost port from where the AX undoubtedly gets its "more powerful than the FX" grunt. It's something it appears we just have to live with, adapting minimum idle RPM and throttling technique to accomodate it. Either that or buy a TT Pro-46?