I got a misfire code 304 ,now I am getting a miss fire code 306 also

could be electrical issues or injector issues. seek diag and est from your mech

The computer is indicating you hav a misfire, that is why it is not running smooth. If you have already confirm the connections are good, then I would recommend bringing it in for professional diagnostics.

Might check exhaust manifold leak or camshaft position sensor

You could have a internal leak on your intake. Are you constantly adding coolant every so often

Mine did this and I had a few cracked injectors. Replaced and codes went away