'95 E320 fuel system/filters

[Glen]

This has been driving me crazy. Several months ago, the fuel pumps in my '95 E320 (W124) wagon started making noise. I bought a couple new Bosch pumps on eBay and installed them along with a new filter. Noise gone...for about a week. Before I change the filter again, the noise stopped and the pumps were quiet for a couple months. Then one day, my wife calls me and says the car died. Forward pump was making noise and seemed to be straining. She was able to get the car safely parked and I picked her up. Later, I went back to check on the car and it started up and made it home...pump making noise.

Ok, so I change out the forward pump again (filter too) with a Bosch unit from a reputable local vendor. Noise is gone again...for about a 4 days.

Should I just try another new filter? Is there something in the system that could be deteriorating and clogging the filters? What else should I check?

Thanks!