I pulled a perfectly good oil pump on the off chance she poops out, I have been running 2 stroke outboards for years and always mixed my oil so it wasn't that big of a deal for me. I wonder if that last cylinder got lean because of blockage in the oil line? Maybe a good idea, if you haven't already, to replace the oil lines with new clear ones so you can always keep an eye on them....depending on who you talk to, those oil pumps are either bullet proof or a ticking time bomb. You are probably better off keeping it since manufacturer thought it was a good idea in the first place. Nice buy on the cylinder parts btw, you might just get away with minimal wallet damage! 8)
On a side note, I think your engine is bigger than mine even though they are the same cc's. Mine is twin carb 2 cylinder so I would assume it's pushing less horsepower at the pump. I didn't realize seadoo put that big of an engine in that small jetski, I bet that thing flew across the water...