Could a bad cat be causing a crappy/jumpy idle?

[lofapoo]

Recently I've noticed that my exhaust stinks like ***, which I would believe would be my cat being darn near dead if not toast already. Could this cat be causing my idle to be kind of rough, and jumpy? It's not a constant issue but it happens alot. When in park (yeah, it's an auto ) the tach reads the RPMs going from the usual ~750 to below 500, at which point the motor shakes the car a bit, then it goes back up, and back down, and back up, etc etc. I've also noticed that when I rev my engine with my lights pointed at a wall they get brighter. I wonder if this has to do with my alternator, or it's the idling issue. I love my baby, I just want her in good clean shape again, so any input is appreciated!

Thanks

[AZhitman]

Sounds like several issues...

Cat sounds like it's toast.MAF needs cleaning, and make sure the contacts are good.Alternator sounds like it's bad.

Those 3 things should clear it up.