I agree with IO540 - The symptoms you described do not seem to me to be a blocked injector as I can personally testify from an experience a few years ago!
I was flying with a glider pilot acquaintance in the other seat - He was doing the flying whilst I was idly looking out of the window - All of a sudden the power just evaporated and there was silence from the front. My friend really was flying a glider now.............
To cut a long story short, whilst looking for the trim, he had turned off the fuel cock which was located between the front seats. When I (eventually - thats what makes it a long story!) restored fuel to the correct place the engine ran like a dog - coughing, banging and generally horrible - It ran so badly that I nearly continued into the field I had selected when we were a glider! After experimenting I found I could maintain height and so continued into a nearby strip.
Upon investigation, all sorts of crap had been drawn through the fuel system and I had one blocked injector and all sorts of debris floating about that may have been partially restricting fuel flow to the other injectors.