you NEED to drive it with the seat off
I was in the same boat you're in, about a month ago... djred and seadoo Lou kept tellin me to keep on it (so did DOC, a 'lil bit)...i literally checked EVERYTHING with the ski off, and i could never find it...even with the ski idling in water..(my problem is, i dont have a trailer, i dock it on a boat ramp)...so finally, being a noob, i had the balls to drive it with the seat off, almost toppled at first, but caught my balance...sure enough, it started pissing outta one of the small hoses that connect to the elbow plugs in the exhaust..it was the TINIEST tear ever and caused a waterfall when running...after i fixed that, i ran it with the seat off again, just to find that one of the "weld buttons" on the exhaust was pissing too, but only when i hit 10-15mph...
So, DO YOURSELF A FAVOR, and NEVER doubt the obvious! i spent DAYS trying to find this problem, so do as minnetonka suggests, ride with the seat off, or at least with the seat on, then CAREFULLY unlip it from the back, and slide it backward as far as you can...good luck