92 740T. Car runs strong when well. A few months ago on a trip it was quitting after a few hours. Determined the main pump was bad, swapped in a thought to be good used one. Ran well til recently but pump is noisy.

Recently with low tank it ran poorly and no noise from intank, so put in a new German one and a new sock. Old sock was black and could see no light through it, but no indication of why it was black, I don't know if that was its natural color, nothing comes off, don't know if this matters but supplying any facts.
I was not there for the final buttonup of the install, but friend says he drove it a couple miles, 3/4 tank, ran fine, and he could hear the new pump working.

Next day I started it, pulled out of driveway, running slowly it seemed fine, but when I gave it gas there was major hesitation. Sorta like someone learning to drive a stick; go, no go, go... parked it, drove it again after a few, same thing over 3 mi or so.
Let it sit, pondered, drove it again now warmed up, seemed fine. ???

Another friend says this is not a symptom of any fuel pump issue he's aware of and to check AMM. I will swap in known good ones, but wanted any thoughts.
Thanks