My Answer is based on clues, symptoms and info in your question. Please include everything. Thanks
Its best to do a oil change, plugs, wires, fuel filter, and air filter at this point. Make sure your tune up is good be for blame parts and wasteing money. Auto zone does free scans so when you get your tune up parts they can test for you real fast. Your more than welcome to bring those codes back to me and follow up.
I have not been paid so Just answer is holding you deposite until you accept or request a refund. I would be happy to let them know of that refund you have asked for.
But there are two things that you may try A new fuel pressure reg will do this and the ECT the engine coolant temperature sensor.
We can continue or i can request a refund. Your the boss at J A