[abuzar1]

New to me 528i. Apparently HPFP and valve cover gaskets were recently changed.

Car ran great when I bought it but had check engine light with Bank 1 too lean code. Guy gave me OEM upstream and downstream O2 sensors so I went ahead and replaced them.

Randomly it would pop up drivetrain malfunction but ran fine so I kept driving. Now it is running much worse. I'm getting Bank 1 too lean, cylinder 4 misfire and P0420 codes.

I thought I'd take off the engine cover to look at the vacuum hoses and replace plugs and coils while I was at it. I've run into several issues

1. One of the fuel lines seems to be leaking. Can I just tighten it up or does it have a seal?
2. I broke one of the vacuum nipples on the vacuum reservoir under the engine beauty cover. Is this reservoir something I can replace by itself or I need to buy the whole cover?
3. The vacuum reservoir was also full of oil and this makes me suspect something might be wrong with the PCV system? Could that cause my issues?