2001 Oldsmobile Alero P0302 DTC

I have an oldsmobile alero that the p0302 DTC comes up. I had to change the head gaskets and all of the other stuff that goes with it. The code started coming up after it was put back together. The car doesn't studder, run funny, fall on its face or anything. You can hear a misfire ever so slightly through the exhaust, but when you drive you cant even notice it, just makes the light come on. I checked the coil already and it is sending timed ignition. The spark plugs are new, so the only thing I can think of would be the spark plug wires may need replaced. They haven't been replaced in a couple of years. So maybe the number 2 spark plug wire is no good? Is there anything else I should check for? What do you recommend I do next?