I've got a 2010 MCX running soft the second half of the slalom course. Runs great with no skier behind the boat, will run 40+ all day long, idols fine, will rip your arms off when getting a skier out of the water. 1st half of the course runs fine gasses fine when the skier pulls but buy ball three when you go to gas it doesn't respond and by ball four forget it. Happens with Zero-Off on, Zero-Off in RPM mode and even when hand driving with Zero-Off off.
I've checked fuel pressure, its 59 to 60 PSI from idol to WOT and when pulling a skier, which I believe is in the range where it should be.
I've got a few ideas but wanted to see if anyone would come up with something different. I wish I had access to a scan tool but I don't.