Is the misfiring constant or random? If constant, locate the problematic cylinder and move the ignition coil to the next cylinder, if the misfire follows, the coil is culprit - if not, then swap the injectors, if the misfire follows to the next, the injector is bad.
If it still remains on the same cylinder, inspect wiring of the injector and ignition coil with a noid light (LED tester), if OK then your cylinders valve seats are burnt out.
You can also do the noid test before unbolting anything to check the electrics.