How can I tell if my Cats are getting cloged?

[Dragonwind]

Is there a time frame when they should be changed out? My 99 has 58k on it and in the Spring it is getting new headers/exhaust. I was planning on keeping the original Cats but when it (barely) started this morning after its cold nap I watched the exhaust and it just kinda seeps out at idle. Is that normal for this car? I am used to seeing a little more of a steady flow from cars.
Thanks,
Chris

[CJ_Boxster]

Well if you look inside it with a flash light once the exhaust is apart, the honey comb inside shouldnt have any blockage. A way i've seen my father test it on other cars is to drill a hole in the exhaust pipe before the cat and if the flow improves alot, then its likely the cat is clogged.

[Dragonwind]

Thanks. Seeing as both sides are identical it is probablly normal. Never the less I am probablly going to put in the Maxflow muffler w/ cats so it will be a moot point. I think I may go with Deluboz's headers though.
Thanks!
Chris

[saaber]

Originally Posted by CJ_Boxster

Well if you look inside it with a flash light once the exhaust is apart, the honey comb inside shouldnt have any blockage. A way i've seen my father test it on other cars is to drill a hole in the exhaust pipe before the cat and if the flow improves alot, then its likely the cat is clogged.

Many exhaust shops will do this (drill a hole in front of the cats, measure with a pressure sensor to see if there is too much back pressure) and then weld the hole. It cost me $20 to do mine on a Volvo.