Have a 2010 HHR with a misfire issue. Code 300.

What is your question?

Change spark plugs, coils have been replaced, fuel injectors have been replaced, mass air flow sensor replaced. Gas cap replaced. My daughter said it started after she put gas in it! I’m thinking it’s either bad gas or compression issue. So would I be wasting my time dropping the gas tank and replace the fuel pump and filter? Or is this another POS that GM put out like the Malabomb!

What makes this problem better or worse?

Misfire

How long has your 2010 Chevrolet HHR had this problem?

Couple months