92 Passat erratic stalling/rough running

I have a 92 Passat GL with the 2.0L DOHC four cylinder with 160K miles and a manual transmission. Since I purchased the car I have replaced the distributor cap and rotor, plug wires, main fuel pump, and the fuel filter. Here are the symptoms I am experiencing: on sunny and dry days, i can drive it without a problem (80 miles), i then shut it off in a parking lot and started it about half an hour later, it idled for a couple seconds then stalled out, I couldn't get it started after that. I checked the inside of my distributor cap for carbon tracking and it was clean, my high tension coil wire was good as well as my plug wires, i checked the electrical connection to my fuel pump and that was good. I turned the key to "run" position and i could hear the priming pump in the fuel tank run. I eventually got the engine started but it wouldn't run at less than 1500 rpms. So i started driving back home in third gear in order to keep the r's up. Whenever i came to a hill the engine would start to stumble. After 11 miles it stalled on me again and would not start, i had it towed the rest the way. When it came off the flatbed two hours later, it started up without a problem and ran fine. The next day was real humid and foggy, this time it would start and idle fine but whenever i put a load on the engine it would stall out or "diesel" until the rpm's came back up i also heard backfiring through the exhaust. Fuel pressure is good, the fuel metering arm that floats in the intake operates smoothly without catching although it does have approximately 1/8" of play at the bottom of its travel before it begins moving the fuel metering plunger. With the engine idling i sprayed the distributor cap, coil, and wires with a water bottle and it didn't effect it. I found a troubleshooting guide that told me to check the ignition coil, all tests passed except for the primary winding resistance test, it had high resistance but the problem doesn't act like a dysfunctional coil. Can anybody offer some insight to this problem?

I don't know if this will help your car, but I put an O2 sensor in my passat and it took care of stalling problems. I think we overlook the O2 a lot because the replacement is 140 bucks. Use an 89 mustang lx O2 sensor. Same sensor, dif plug. All you do is solder it in to your old plug.