please help this mechanic 2.2 p0300

I got a 97 cavaleir 2.2 p0300 random misfire. I've changed plugs, wires, fuel filter,coil packs, crank sensor and ign module as well as 2 leaky injectors with new ones, and I can still see the spark mising through my spark testers. Could the injectors that I bought be at fault? That wouldn't make the spark intermittent would it. I feel it is a spark problem as I can see the spark cutting out. , and I can still see the spark mising through my spark testers. When I have the testers on there normally they spark fine but you can see that it is intermittent in the cylinders. I am looking for what if anything would be causing this code 300. PCM?? I can't think of anything else to try. Please help this mechanic. Any common problems that anyone knows would be greatly appreciated