'93 240sx electrical issues, please help!

[s13_gearhead]

Ok, so here's the problem.

Just converted my '93 Nissan 240sx coupe to 5spd, but I don't think my electrical issues are swap-related. I posted previously about this same car having dash / interior electrical problems, and those have been fixed; there were two plugs on the fuse box that weren't plugged in at all. Done.

Now what's going on is this... I can start the car, and it warms up just fine, no problems at all. When it's warmed up and I give it a little cash to drop the idle down, the car stalls out, and dies. The revs drop really low the more I open the throttle, and when I eventually do get off the accelerator peddle, the car will continue to rev lower and lower, until it finally sputters and shuts off. I turn the key to the off position, and I get a buzzing noise coming from the engine compartment.

I've tracked the buzzing now to the relay/fuse box behind the battery, and subsequently to the EGI Relay (See Photo). It makes a wierd buzzing sound and vibrates, and the sound won't go away until I either pull the relay or disconnect the negative battery terminal.

I've checked all the wiring on the transmission harness to make sure there isn't a pinched/crimped wire somewhere, and it all seems to be fine. All the sensors, as far as I can tell, are plugged in correctly and the vaccum is run properly.

What is going on, guys? Help! I have to sell this car and I can't get it running right long enough to pass a smog inspection, or even think about driving it to a smog tech. Anyone have any ideas??