Code PO304 # 4 plug misfire

Hello all,

My code reader is showing a P0304 - #4 plug misfire. Ie changed spark plugs (shop tuned it and did the work) Ie checked the gap on the plug pulled the spark plug wire and can see a good spark flying from it. yet it is still misfiring.
I put a compression gage on it and getting 120 to 140 PSI. And I out of ideas. I do not want to take it to a shop untill I know what they need to do with todays prices to just start searching untill they find it.

Any pointers of what to look at next? Please!

check the ignition coil

If you're getting good spark it is probably the injector. (either clogged or not working properly) Run a bottle of injector cleaner through and see if that helps.