My 1994 Mercury 225 carbed will start and idle fine. It will run perfectly above 2500 RPM's when you idle up above 1100 RPM's and below 2300 RPM's the motor will slit and pop and then cut off. I have put a new stator problem still persist. I have put a use ecu on and the problem is still present. I have put a new TPS on and it still persist. My Mechanic said the carbs neede rebuilding, problem still here. I have checked the timing with a timing lite and the timing is not advancing. Any suggestions.