1994 Cadillac STS car stalling

Put a fuel pressure gauge on and verify it loses pressure. Does it stall when coming to stop, and just like the key is shut off. If it was losing fuel pressure, it would gradually lower and die as pressure in the fuel rail falls below threshold for running. If it shuts down immediately, I would lean more towards electrical. Does it still have original plug wires(the have cylinder #'s on them)? If so try replacing them, they can break down to the point where the ignition module shuts down. Also, if this occurs typically after cruising speed, you could also have a sticking open egr valve.