So I woke up my 82 12A GS after the long cold snap, it was a little flooded but I cleared that up and she started within 30 seconds of initial crank. The gas in it is gross and old with outside temperatures ~0 celsius, so I left the choke open full. Came back a few minutes later to see how close it was to warming up. Noticed some smoke from under the hood, but very little so I went around to pop it open, glanced at the dash, with choke open idling at around 2,000rpm, engine temp at about 1/4. When I popped the hood I noticed the smoke smelled like exhaust, directing my attention to the red-hot down pipe. I shut it off immediately, checked under, red hot for most of the exhaust.
Next day I topped up the coolant levels (the reservoir was low but the rad was full) and started it again, same thing, choke out and idling at warming temperatures. Not 5minutes later noticed the beginning of smoke, checked the down pipe from above and it was good, got low and noticed the heat was coming from the cats. I snagged a picture

Engine temp here wasn't even off the cold line.
I noticed a distinct popping sound every couple of seconds followed by a slight drop in rpms, I assume it's because of choke not being spot on to the richness that the engine wants. The popping happened before if I remember correctly, it went away after the engine was warm or revving past 2,500 rpm. It never set the exhaust up like this.

So has anybody seen this before? What is causing it? Boned cat? Defunct plug causing unburnt fuel into the exhaust? Both? I swear, gremlins are messing with me. Please help!

 

Most likely causes are retarded timing (possibly due to loss of leading ignition or fouled leading plugs), or a restriction in the fuel system causing a lean condition (not likely since you had the choke out.

Check out the leading plugs, make sure they're not fouled and verify that they are sparking...



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I went out to the car today, found that one of the leading plugs connector was bent a little, i got out my extra battery and clamped the positive to the bent back end and touched the negative the center electrode. No sparks! This is probably what has been causing all my problems as it was probably in the trailing position, causing random flooding.

 

Red hot cats make great hand warmers in the winter. Since they got that hot, it may be time for them to go. The choke should have pulled off by the time the temp reached 1/4. It most likely is the leading ignition that failed since the car has sat and timing doesn't change on it's own. Put some fresh gas and Sta-Bil in the tank.

 

The engine wouldn't even have to be warmed up to produce red headers. I agree, it is probably the leading spark that you are missing. Make sure you don't have the trailing ignitor firing the leading plugs (happens sometimes if coils get switched around, etc.)...

 

that is a killer picture