Had a similar problem on my 1990 turbo model. Would be cruising down the interstate and engine would just shut down. Got to were I couldn’t trust the car. Did all the usual 7 series troubleshooting, fuel pump relay, grounds, etc. Ended up being an easy fix. There are multiple red power feed wires going to positive battery terminal and the factory crimp was randomly losing connection, even though it looked clean and tight. Cut all the wires back and installed new, good quality battery terminal and that corrected the problem.
Also had a 760 towed into my shop with same complaint. Ended up being in the fuse box, one of the spade connectors under the white fuel pump relay had pushed out of the block and was making intermittent connection to relay. Car would run fine, then just shut down leaving the poor guy stranded somewhere.