My previous post may have been overlooked. Once again, I must ask: does anyone suspect a clogged or partially clogged cat? 10 years ago, My 86 VW Golf suddenly died once, as if I shut the ignition key off. I was able to start it up again; it idled poorly but would smooth out as RPMs increased. It would run but was extremely underpowered and could barely make 40 mph. I had just replaced the cap, rotor, wires, plugs, and fuel/air filters, so those parts weren't suspect. Don't ask me why, but for some reason I suspected an exhaust blockage problem and checked for exhaust outlet at the tailpipe - it seemed really weak compared to my other running car. I jacked the car up and noticed exhaust pipes from the cat forward were very hot (though not glowing red like yours). Pipes behind the cat, although warm, were much cooler. I cut the cat off and looked inside. The honeycomb-like catalyst had somehow shifted within the housing and was partially blocking the exhaust flow. It actually looked like it "shrunk" or got eroded away to a smaller size so that it was no longer snug in the housing, and it rotated. Who knows - maybe rich mixture dissolved it? I don't know... Anyway, replaced it with a straight pipe (I know - illegal) but the car ran normally again. Sold the car 6 months later due to low oil pressure.

I'm not saying this is your problem, but it sure wouldn't hurt to at least look into it.

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