So I have a 93 civic. It runs great when you first start it up and the block is cold, but as soon as the car starts warming up, after about 30 minutes of driving, it gets really bogged down, it doesn't want to accelerate past 30mph. It's acts like it is clogged. I thought that maybe the catalytic converter might have blown up in the thing, but I haven't confirmed this for sure yet. But it might make sense... i mean cat heats up, then clogs, causing backpressure? I don't know what does everyone think?

its possible. have you tried to remove the cat to see how it looks inside?

I would punch out the cat or order a test pipe off ebay about $40 should fix the problem but to just check make your your not throwing any ECU codes

Well I popped the car up on jacks and tapped my cat with a rubber mallet. I definetely think its the cat now, sounds like broken glass or something inside the catalytic converter. I took a sawzal and sawed an opening just before the cat to relieve the pressure until I can afford to get a new one. Although I don't know if that is that great, any chance I'll get backpressure in the engine and blow it? I mean this isn't an old muscle car v8 where you can run open headers.

lol that's not how it works. it'll be fine. you can run the car without headers as long as the 02 sensors are working. the only issue you could possibly have without running headers if it you literally run NO headers and cold air can hit the exhaust valves and bend them