I'm glad you found a culprit hopefully that is the only issue. I haven't had problems with mine since I found my stuck accelerator pump check valve. Maybe you will luck out and itll be one of your outside main bearings going bad for an easy and cheap replacement. I have found cylinders for...
Lessons I have learned, I not a seadoo guru but have learned a lot of lessons the hard way:
*genuine mikuni kit*
If you replace the seat and needle valve buy the right size and the right spring to get correct pop off pressure mikuni has charts for spring to seat size. NEVER chop the spring...
I had the same thing happen on my 720(single carb). I rebuilt the carb with genuine mikuni kit and was still having lean issues between 2k-4k. After a lot of troubleshooting, checking fuel pump, removing inline fuel filter and rechecking pop off pressure i realize that i had been neglecting one...