I have a two cycle 45 hp ultralight engine on an airboat. I did not change my prop since last year and I have dropped 300 rpm's that I can get full throttle. I was getting 5900 rpm which is where it is supposed to be, now I can only get 5600, sometimes 5650 rpms. I cleaned carbs, synced them, etc. Exhaust pipe runs cooler also. We swapped carbs, swapped spark wires from the other side, same problem. Compression is good, did a leakdown test and that's good. New spark plug also. When I accelerate the CHT on the bad cylinder will momentarily drop, and the muffler runs cooler than the other side, but CHT gauge says they are the same when idle. This engine was just rebuilt by someone who has been repairing small engines for quite some time, but he is baffled by this also. The engine only has 20 hours on it since overhaul. If anyone can help please do! Thank you so much.