Is it possible for backfire to blow out the honeycomb in the catalytic converter? My FD usually backfires normally when cold, but one morning, it backfired unusually loud (the **** actually startled me). Didn't really think anything of it until the next morning. When I started my car... the idle sounded off. It had more "staccato" to it. And it came from the exhaust tips, so I'm pretty sure it's not a leak. Upon driving the car the exhaust sound really didn't sound all that much different, but I think I noticed a slight rise in boost, making me think that there's less backpressure. Hence my hypothesis that part of the cat blew up. Has this happened to anyone else? By the way, I also have a pulley kit with no air pump, downpipe,N1 duals, intake, if that makes any difference.

 

No air pump? I'd imagine that's the trouble right there. You can't run with cat(s) and no air pump or you'll quickly clog and/or destroy your cat!