MadScience_7

Possibly. I need to do some tearing apart before I know for sure. At this point the symptoms are that the car is much quieter than usual, and it doesn't want to rev over about 4k under load. Whatever happened, happened when getting on the interstate. I do remember seeing a big puff of dust or something behind me at the bottom of the on ramp. I thought I must have hit a patch of dirt without noticing it. After cruising for a while, it came time to get up to speed and pass someone. When I downshifted to 4th, it started misfiring and the AFRs showed between 9-10. Obviously something was wrong. When I got to my destination, I tapped around on the exhaust and the cat sounds totally hollow and the mufflers sound like they're packed full of something. I was able to limp it home, albeit with an effective 3.5k redline and only about 40 useable HP.

As far as current parts go, a couple years ago I replaced the main cat with a generic OEM cat. Headers are Corksport. The cat-back is some aftermarket brand, possibly HKS.

My current assumption is that the cheap cat finally came apart and all ended up clogged into the mufflers. If that is the case, I would assume all of it is scrap. I don't want another cheap OEM cat, but no way in hell am I paying $1500 for a new Mazda part. Bonez cats seem to be popular, but I can't find one that is a direct fit. I think I am going to get RB exhaust, but only the cat-back since I already have headers, and I need to stay emissions legal.

Any other suggestions for a new header-back system?

Thanks
Andy