On my 94 e320 Wagon: my fuel pumps are original and they [or at least one of them] make a high pitch noise that I understand is normal. I have to have ear close to wheel to hear it. When standing up, my 60 yr old ears don't hear the noise. It's been more than a year since I changed fuel filter, so memory is a little foggy. But if memory is correct, there is minimal hose to detoriate and although metal lines can look terrible on outside they're quite durable and not likely to detoriate inside.

The durability of the fuel delivery system and your comment regarding the codes makes me think your problem might not be fuel delivery.

If you're using Arthur Dalton's Code reader; you can read codes from pins 1, 8 & 14.

Knowing the specific pin/code combo will make it easier for others to help you.

I'd pull codes for all 3 pins then check part # of OVP. OVP is behind battery. Easy to do if you remove battery, but you'll clear some codes when you disconnect it. 10 mm nut / bolt secures OVP bracket. Makes it easy to read part #.

Has main engine harness been replaced?

Bob