Humming in speakers, then engine died

I have a '97 Explorer, 4.0 OHV, just turned 90,000 miles and have had a funky problem happen twice now. Once last night and again this morning. I start the truck and let it idle for about 10 minutes. I then go on my marry way up the hill to the red light light with the heat on high and a CD playing. I then have to merge into traffic and hit the gas as usual, WOT. Well last night and again this morning as I give WOT the speakers start humming. I turned off the radio and the humming was still there until I let my foot off the gas. Then the humming goes away after 10 seconds or so. As I come to the next stop light about a quarter of a mile since merging, the engine dies as soon as I stop. Restarts right up and I have no problems after that. What could cause this? I have upgraded everything in the past year, 900 amp battery, new alt, IAC valve, plugs, wires. Could it be the cold weather? It was -4 last night and +3 this morning so said my temp in the overhead console. This is wierd. Any help would be great, thanks......