My check engine light has been on going on two years now. on 2007 Chevrolet Cobalt

It codes as a cylinder 3 mis-fire. I had all of the spark plugs changed and the check engine light is still on. It took 3 inspections before it finally passed. When the gas tank is full It feels like it runs better and I don't feel it misfiring. Has anyone had any experience with this?

Asked by for the 2007 Chevrolet Cobalt
2 answers
Possible weak fuel pump, have seen that before.
try a higher octane gas next time you fill up.