uneven rpm readings
 

I have twin 500 efi's and through the rpm range therer is a 100-200 rpm difference between engines. I am running B1 drives in a twin step lightning and they are turning out. Engines have 300 hrs. I am at 5200 @ wot on star and about 5050 on port. Down around 4000 it is about the same. Even as low as 3000 there is a difference and its always that motor. I've checked trim settings varying each drive with no change. Ive changed props and nothing. The motors run strong up through the range pulling well.

What else could it be other than a sender or gauge issue. I guess there could be resistance in the drive looks like that would make some kind of noise. The drive oil looks great. The engine fluids look fine.

Any ideas?

Most likely the tachs are off. Put a scan tool on it to verify. If they are correct it could be throttle linkage. Worst case is one engine could be down on power. You've already proved it's not a prop issue.