engine electrical

Hello, I have been reading various posts around the forum to learn more about care, maintenance, upgrading and repairing my Traverse. I am running into dilemma I am hoping someone might be able to give me some advise on or had faced a similar problem and can let me know how they handled it...

I am having trouble resolving trouble code P0304. I am going to provide background information which only dates back 6 months when I purchased the 2009 Chevy Traverse 2wd with 134,XXX miles and a P0305 and ?P0420? fuel pressure too low bank1. I don't exactly remember the code. I replaced the...