Random misfire problem

I have a 1992 Pontiac Grand Prix that is having problems. I tend to lose the electrical power to two of my cylinders on a regular basis. It generally occurs after the car has warmed up. I have tested the wires with a timing gun, and found that I lose power to cylinders 2 and 5, as this is a DIS system.

I have replaced the entire ignition system–starter, plugs, wires, coils, ignition module, crankshaft sensor, and ECU (in that order)–but the problem persists.

I am at my wit’s end trying to figure this out. Any help would be appreciated.

The same ignition coil serves #2 and #5 spark plugs. Since you’ve changed the ignition system components, all that’s left is the wiring between those components.
Now, you need someone experienced with wiring to do a careful check of those wires and electrical connectors ----- including grounds and ground wires.