Please help

A misfire is pretty straightforward to diagnose.

1. Switch the spark plugs between the dead cylinder and a cylinder that is firing, and see if the misfire moves, if it does, you need a plug, if not, keep going.
2. Switch the spark plug wires (if applicable) between the dead cylinder and a cylinder that is firing, and see if the misfire moves, if it does, you need wires, if not, keep going.
3. For Coil-On-Plug, Coil-Near-Plug, or 2-plug coil systems, repeat the above for coils. For single coil or coil-pack systems, test the coil using a multimeter and the specifications chart from the manufacturer.
4. Switch the fuel injectors between the dead cylinder and a cylinder that is firing, and see if the misfire moves, if it does, you need an injector, if not, keep going.
5. Use noid lights to confirm you are getting a pulse to the injector on the suspect cylinder from the PCM. If not, use a multimeter to check for continuity through the harness from the PCM connector to the injector connector. If continuity is good, replace the PCM, if not, repair or replace the wiring harness. If all is good, keep going.
6. Perform a compression test. If the compression is low in the suspect cylinder, perform a cylinder leakdown test to see why. If it's high, remove the valvecover and inspect the valvetrain.

Seeing as you've thrown all of the parts for steps 1-3 at it, you're at step 4.