[mark houghton]

Fuel pump(s) is where I would first look. Since you can't seem to keep her running long enough to diagnose, try replacing both pump relays (minimal cost, and it's always good to have spares even if that doesn't solve your issue).

Depressing the metering plate is at least causing the pumps (or maybe just one pump) to run. How about unplugging the metering plate switch blue connector (or is it green?). That will result in your pumps running continuously with just the key in the on position and the engine not running. You'll hear the pumps run....pull one relay at a time and see if any difference in the sound that may point you to which pump may not be running. Also, unplug the wire to the overboost sensor and ground it, just to make sure that's not the culprit (a poor or intermittent ground will keep both pumps from running). Gotta be methodical, one thing at a time.