2001 Ford Windstar Engine not running on all 6 cylinders

Hi. I've got a 2001 Ford Windstar, 3.8 V-6, with 100K miles on it. It has always started and ran fine. I live in Northern IL, where it's cold, so I usually start the van and go back into the house until the van is warmed up. The other day I did this and the van started fine and sounded fine, but, when I took off it had no power. Computer says bank #1 rich. Changed plugs and wires (old ones looked fine). Compression test shows 160 lbs. Have spark. Injectors are all working. No vacuum leaks. Pulled valve cover, every things o.k. Pulled upper plenum and could see no problems or cracks. While engine is running I've pulled wire off of #1 injector with barely a difference in the way it runs. Injectors are getting a pulse and with a fuel pressure gauge attached, is showing pressure loss when injector is energized. Rotten smell from the exhaust, confirming rich fuel. Also, while the engine is running, there's a (what sounds like) muffled explosion (popping) in the upper plenum. Check Engine light is on. Any ideas ?
Thanks, in advance, George