RED HOT behind left precat...

[L.O.R.D. SVX]

... after idling for 5 minutes. Somethings up with my car. I can't figure it out. Let me just bullet all my symptoms and we can go from there.

-Exhaust note sounds grauggy (like a small pickup with straight pipes, louder but lower toned) after warming up
-lost of power after the exhaust note changes to mentioned above
-code 37
-running hot on the left exhuast (all white on the inner walls of exhaust)
-looping idle at times
-weak idle other times

At first I thought it was something to do with my cats. So I switched my precats and main with my other SVX which I know is perfect. Turns out it act the same as before. Code 37 did pop up after awhile too (these are the O2s from the other car, not the same ones). I did reset the computer to clear trouble codes before this.
As for the driving experience, when I let it sit for a day or two then drive it, the exhaust note sounds sooo sweet. Then give it a good warm up, the exhaust starts to sound like crap and power starts fading with a very bad idle. If it was a cat problem, the sound should become more muffled, right? Not mine, it gets more louder.
And just recently, I noticed the car smoking a little from the hood when I fired her up in awhile. Behind the driver side precat was glowing red (during the day) while just idling for about 5 minutes. Only the rear part of the precat (the transition from the full size of the precat to the pipe in between the pre and the main) was red hot.
Could this be a fuel problem? Running lean on the left side? How can the precats get to that point so quick, so quick the car didn't even warm up yet.
Could one of the Gurus on here help me out, PLEASE. Thanks.