Does this sound like a fuel pump relay problem??

[MikeTangas]

Driving to work this morning on the interstate doing about 75 MPH, while passing another car there was little to no throttle response. My first thought was fuel filter because I am approaching 30K on the filter. Instead of passing I let stayed behind the other car then all of a sudden the engine started losing power. I was able to limp to the next exit at maybe 40 MPH but the engine was running rough.

Got off at the exit and at the stop sign the idle was fine. I went over to a parking lot and sat there idling for a few minutes, everything fine. I continued to work by way of secondary roads, car ran fine. Could only make about 60 MPH on these roads, due to the roads not the car. Then after making a turn and accelerating, coming off a stop light, I get lit up by all the idiot lights coming on...the engine had shut down. Coasted into the next parking lot and stopped. Sat for a minute, hit the key and the engine came to life. I then drove into the office without problem.

Weather conditions this morning were light snow and 20*F at 0530.

None of the fuel pump relay posts I dug up in the search mentioned anything about "at speed" problems. Nearly all mentioned the sudden stalling at, or coming off a stop.

Instinctively I am leaning toward a filter and a fuel pump relay. Anything else I should be looking at?

This is regarding the '86 560SEL.