My guess is a clogged cat as well. Sounds like heat from the exhaust is not flowing out as it should. THat back up is over heating the manifold (hence the glowing red color). And since the car is not "breathing" right, that is why it's starting to give performance problems.

If you have to replace the CAT, I would suggest a ZZP downpipe with high flow cat. It's a little more in price, but if you have the tools, it's an easy DIY (bolts right in with no problem).