If the fuel pump sounds bad, then this should be the place to start, it could be fuel starvation (so I would keep it off boost)

Re the hunting, you can try cleaning the valve, but I have done this and the problem still persists.

I tried an aftermarket valve, but this made the problem worse. You can't get hold of the OE valve, mine has always done it, so just got used to it, although it is annoying!

Also as it is new to you, I would advise you check the fuel pump and fans have been rewired.

Martin