Have the same engines and had the same issue. High Wire could be on track - my problem was that my tachs were out, so Port engine was burning a lot more fuel by physically running at a bit over 100RPMs higher than Starboard even though tachs were showing same RPM's. It was carrying more load.
Get a photo tach and check. The old tachs are never accurate across the range though. I set mine as "most accurate" around the 1500RPM mark as that is where I spend most time. At idle they are still showing around 100RPM difference.
Not saying it is your problem though but always worth checking.
I refuse to engage in an intellectual battle with an unarmed man. (unknown)