2013 Yamaha 242 Limited S - Engine RPM Mis-Match

[Offseason]

2013 Yamaha 242 Limited S

Port side engine started vibrating and lags behind the Starboard engine by 1,000 RPM when cruising over 20 mph.
Port side engine sounds much louder than starboard engine at idle and while cruising.
there are no alarms or "check engine" lights

Things I have tried / inspected:
Seafoam in the gas (2 oz per 1 gal) drove around the lake for an hour - no change
pump obstruction - no
spark plug gap - .031-.035"
fuel injector ohms - in spec 11.5-12.5 ohm
swapped 4 coils from starboard engine - problem did not change
cam position sensor - input 4.99V and output in spec (screw driver test in service manual)
all fuses good
removed port side fuel pump and inspected inlet filter (good) and looked in fuel tank (clean)
inspected air filter - clean
APS (accel position sensor) - APS1 was .93 Kohm closed / 4.67 Kohm open - this is slightly out of spec which is .5-.9 kohm closed and 3.75-4.35 Kohm open

running out of ideas
I ordered a fuel injector tester - has not come in yet
I ordered the Yamaha diagnostic software and harness - has not come in yet
I ordered spark plugs (common recommendation on forums) - has not come in yet

anyone have a similar issue? what did you try?

 

[Babin Farms]

Vibrating like it's cavitation?? Did you pull the Port pump to verify nothing is in it? Sometimes something as small as a toothpick can get wedged and you can't see it or feel it without pulling the pump.

Did you change the spark plugs?

 

[Offseason]

I ordered spark plugs but they have not arrived yet,
I spark checked all four and sure enough 1 of them was dead.

Replaced the bad one and Engine runs fine now on the hose, will try to get out on the water this weekend.