95 Aurora Rough Running

My 95 Aurora just started running rough, particularly at Idle.:disappoin

I noticed the rough running so I was checking it out in the garage.
All of a sudden smoke started pouring out the engine compartment.
I determined the smoke was coming from the CAT, ie it is plugged.
I changed the CAT and it still runs rough.:screwy:

Anybody got Ideas of what to look for.
I am going to go over it this week as I have some time off.
I would appreciate any and all advice.

Thanks
Mark

yep: codes? or no codes?

How did you Know that the cat was bad

Look through the old cat..... Can you see light through it? Smoke off the outside of a cat is an oil leak or water leaks not a bad cat. There are only 4 ways to tell if a cat is bad. 1 you pull it and the car runs fine or you check for high pressure before the cat. 2. You look through it and it looks like the holes are plugged. 3. The darn thing caught on fire. It is clean as a whistle and just wont pass an efficiency check.

There is a tone of things that can cause it… try a real tune up first. I am always impressed of how many cars with as many as 80 thousand miles come in with the original plugs and wires………… If I could sleep at night I would be rich