Misfiring error on various cylinders

I have replaced all spark plugs (gaped to.060), spark plug wires, including center high voltage wire, distributor cap and rotor. I get various misfire error readings on OBDII code reader. 305 error, 306 error, 300 error. After erasing errors and allowing engine to run, I might get another 305 error (misfire on cylinder number five) or I might get a 300 error (multiple cylinder misfires). I rechecked fittings on both ends of all spark plug wires and have checked each wire (close to spark plug head) with spark plug wire tester light. All wires seem to be causing the neon test light to flash regularly. The engine has hesitation during take off, like it wants to bog down and decreased power and of course thee 30x error code(s) come back while driving or idling. Replaced air filter. No effect. Please advise as to how to diagnose further.