XL700 Stalls at High Speeds

[GarysXL700]

I have an issue with the ski stalling at high speed and I have to work the choke to keep it running. I have rebuilt the carbs once and getting ready to do it again.
Any other suggestions?
Could you also help explain the carb settings as it shows -5/8(M) and 1-1/8(P) adjustments. What and where are the "M" and "P" valves?

[SBT-Tech 2]

Re: XL700 Stalls at High Speeds

the M means mag. carb or front and the P means the pto carb or rear carb