How to fix a check engine light with code P0302? And Pass Oregon DEQ? on 1997 Mercury Sable

I check the code it pops up P0302, misfire on cylinder 2. I had Spark plugs check and coil changed. After code still pops up. I had a shop do a test to find out what the cause is and was told to check with Ford Dealer. I have good combustion, air flow, gas, ignition. They couldn't find out. I did not take it to the Dealer for the ridiculous price to diagnose. When to a second shop said the same thing. When I had the tune-up the car didnt bring the code up till miles later then recently code P0302 and P0303 code pops up. Reset the computer the only code after 5 miles pops up is P0302. I cant pass the DEQ with the check engine light on.

you have a misfire in cylinder 2 and 3 recheck pluges and wires
I checked that still persistent. Cylinder 3 had rusted and blown spark plug. Can 02 sensor cause misfires.
no o2 sensor wont make any difference
1 more answer
Hello dear costumer the cause of misfire since you check all the thing you mention injector or burn valve or bad valve spring or damage head gasket between # 2 and 3 and get coolant in the compestion champer or bad TPS