It is a new boat to me, I did a water test on it back in March when I bought it from dealer and even when I put it in the water yesterday it ran fine for about 3 mins without a miss. It did however seem down on power. Even a no load free rev you can hear the miss. I forgot to take compression tester to the lake but will take tomorrow to at least do the left bank if I can get my hands in there. Only have a 2.5in gap between exhaust header and hull.

w/ the boat running isolate the bank that is popping and start there.then if you can feel the bottom of the exhaust manifold,find the dead cylinder/s.
just fixed a 525efi for a pop thru the exhaust,1 was spark plug strap got pushed into center electrode.other 525efi had a valve guide stick and slightly tapped valve,that required head removal,guide work and a new valve.good luck and keep use posted,,hope its simple.

And on the scan what did available power % SHOW ???

It's been awhile on this. Any conclusion??