Hi, sorry to hear about your problem. Do you get the misfire at 2700 rpm under load, or parked? Sounds like it could be the fuel injectors - when you say you cleaned and checked them - does that mean you removed them? Did you examine the o-rings around the injectors to see what shape they are in? You can carefully spray carburetor around the injectors to see if the engine reacts (maybe spraying water or a smoke test is safer).
Good luck
-Jerry