p0420 code, engine will not rev above 4000 rpm
 

2004 T&C 3.8 110,000 miles I did some searching but couldn't find any threads with my exact symptoms. I was driving home last night when my CEL came on. Did the key on-off combo to get the code P0420. I planned on changing the downstream O2 sensor first before looking into a new cat. Nobody had it in stock, so I placed it on order. In the meantime, I disconnected the battery to clear the code. Afterward I cranked the engine and it seemed really sluggish. I reved up the engine and around 4000 rpm it acted like it hit the rev limiter and there was smoke coming out of the exhaust. I drove it around the block and it drives fine and pulls hills fine. However, when I was driving I never hit the 4000 range. Does this sound like a clogged cat? Thanks for any advice.

I reved up the engine to around 4000 rpm to check the back pressure with my hand. It seems like a decent amount of exhaust is coming out but its hard to say with out something to base it against. However, when I looked at my hand I saw flecks of silver metal on my hand that had come out of the tailpipe. I have one other question. Do you have to have a welder to replace the cat? I see the bolts on the front of the cat but it looks like a weld on the rear.