cylinder 3 misfire?

I have a 1997 lexus es300 with 80k miles. Last week,it started idling low, so I hooked up the OBD2 scanner. It stated cylinder 3 misfire.

I have changed the sparks plugs, spark plug wires, and tested the coil(switched coils). It still idles low and still it states cylinder 3 misfire. I have run out of ideas. Any other suggestions that the problem can be?

I have a 200 ES300.
PO306.
same situation as yours.
Flip-flopped 2 coils.
Replaced what seemed like a dead coil.
Same problem.

A month ago the Iridiums plugs were replaced with regular resistor type NGKs.
I am wondering if this caused damage to the ignition system.
I know with older Mitsubishi vans failure to use the Platinum plugs resulted in ignitor failure, or injector problems.

I am going to try putting back the iridiums and see what happens.

Is a 96 OBD2? I need to pull some codes, Im having a poor idle and milage problem and sometimes I can smell fuel but found zero leaks. Could this also be a bad cat or 02's?