Ok, is tihs supposed to look like this

[73k5blazer]

This cat is only 1 month old. All of a sudden the thing is hard to start, is fouling plugs right & left, blows a little black smoke. At high RPM it's fine. Idle is ok, but it could be smoother. it's the middle rpm range that is troublesome. Gas mileage as went to the dumper. It put a new carb on about 4000mi ago, it ran perfect until last week when this started happening. It feels like it's missing. So I put a new cap, rotor, coil, plugs, wires. It need all that anyway. It didn't help.
So in poking arond I see this. Is this supposed to look that way?

 

[mouse]

The cat looks fine to me. Check timing, and for vacuum leaks. This is always a good place to start. Have you done anything else lately?

 

[2Dogs]

Getting too much fuel for some reason - might want to check the new/rebuilt carb....?

 

[73k5blazer]

Nope, the exhaust last month, and the carb about 3-4 months ago. That carb ran perfect out of the box for 3200mi. I think it is getting way too much gas though and the unburned fuel is burning in the cat. Don't know what happened to that carb to cause it to all of a sudden start running rich. At high speed/rpm its fine. At low RPM I just yesterday adjusted it to me fine with the idle mixture screws. At mid rpms it's acting like it's missing. When Iswapped the plugs yesterday they were smoke black. It blows a little black smoke too. Guess I got my weekend project...