Chevrolet Repair: 94 chevy s10 blazer, chevy s10 blazer, s10 blazer

Question
how do you tell if you have CMFI or MFI injection? What would cause an injector to put to much fuel in two cylinders? I have my 94 chevy s10  blazer 4.3L engine in a shop its been there over a week they said two cylinders weren't firing now those two cylinders are getting to much fuel? Last month I put a new fuel pump and sending unit in. Hope you can help.Thanks!

Answer
Pretty much just bad injectors, or a short in the injector wire keeping it open.
If the two cyls are not firing, then the fuel will accumulate in them, and look like they are getting too much, when actually they may just be not burning what they get.
Van