Engine Mechanical problem
2002 Toyota Rav4 4 cyl Front Wheel Drive Automatic 135,00 miles

I have a check engine light constantly on. I took it to the auto parts store who has a gauge or whatever it's called that reads the check engine light. It says that theres a misfire on cylinders 1&2. They say that it's either the spark plugs, coils, or injectors that are bad. I have replaced all the spark plugs and have tswitched coil 1 & 3 with each other and it still reads there's a misfire on 1&2 so I figure that the coils are fine. Do u believe that this anlalysis is correct and that it is indeed the injectors?

Also on a seperate note what is the 4 spark plug looking "things" that are attached to whatever it is just below or in front of the engine block. They have wiring which at the end has a clip that is clipped into another clip. Thanks