hard starting issue 2006 VED12

I have gone through the earlier posts on hard starting. I have a 2006 vnl780 with the VED12 465. It has 809,000 miles. About a month ago it lost power and could barely make the slightest grades and started hard starting. I put fuel service through it and got most of the power back maybe 80%. My mileage is down partly because i'm reluctant to shut it off except where I could get help if needed but I believe my driving mileage is down also. I use to be at 6.1 now down to 5.2. I do get an occasional code for fuel pressure, a couple times while driving and a couple times while idling.
I've had all 4 batteries replaced, and had a full service. Hot or Cold, it turns over so long that I'm afraid it will drain the batteries before starting. When it starts, it does so gradually.
I've contacted several volvo dealerships and the service managers seem to agree it's bad injector. They say the injector cups were copper based and those are no longer available that the replacements are stainless. Therefore they say I can't just have the bad ones replaced but must do all 6 at a cost of around $6500. I think it is odd that none of them talk about check valves, or a weak fuel pump, or sensors, or wiring harness but rather jump right to injectors and cups.
was there a recall on the injectors for that engine?
This thing has been a nightmare, I have spent 25,000 in repairs in the 2 years I've owned it. Had to have both EGR's and the cooler replaced 2 weeks after purchase, then the lower front engine cover developed an oil leak...that repair went almost $8000. The A/C pump had to be replaced both summers. The oil pan had to be replaced as a crack formed from one of the mounting bolt holes. The crank sensor and harness were also replaced.

 

Thanks, i'll press them to look at the fuel supply Sorry I don't see how to register a "thanks"