912is rpm drop when shutting down lane B

[jorgy]

if I shut down lane B the engine will lose approximately 1500 rpm and run rough. i have no lane faults or fuel pressure issues.
if I shut down just lane A, the engine gains a few rpm's as expected.
in recent flights i have been experiencing rising EGT's on cylinders 1 and 2 but i can keep them around 1600 if i throttle back to 4700 -4800. all of a sudden that will clear up and the engine will run perfect and the EGT's will drop to 1400 for a little while but then it comes right back. you can feel that the engine isn't running perfect during the rising EGT period.
when it clears up, the engine is crisp and smooth as silk.

As I said, there aren't any lane faults, fuel pressure stays around 42-44 psi.

any ideas where to look?

Jorgy

[Sink Rate]

I'm certainly not an expert, but I would venture a guess that your cylinders 1&2 might be a bit fuel starved. Perhaps blocked injectors? What makes me doubt my own answer though is that it occurred on two cylinders at once. Do you believe in coincidences? How many hours are on this engine and what is the MAP when you reach 1600F at 4800rpm?

Where I fly, the MAP never reaches 25inHg due to the altitude, and the highest I ever got the EGT to is 1527F on the two rear cylinders. That was in lean mode at 98% throttle position and 23MAP.