No Joke!!!!! Black flag that one and replace the cats quick! You only do more harm than good trying to drive it with bad cats! Put it this way....The night I found out my 84 cavalier's cat was bad, I called dad to ask why was my exhaust manifold GLOWING RED!!!!

Driving fast??? Depends. How much RPM are you turning? Think about this. A cat hardcore metals in it. I forget the main one and the reason why cats are expensive. The reason a cat gets "clogged", as it was explained to me, is that the metals melt and then restrict the airflow causing it to clog. Do I think that hardcore driving will lead to cats failing? Maybe, maybe not, but down the road they may cause them to fail a little earlier than normal. But this can be said of anything that fails early.

L8R
Rich

'96 Mystique, Zetec, MTX.
---Mods---
Removed both intake resonators and airbox. Installed APC air filter and APC crankcase ventilation filter. Removed exhaust resonator.
Installed XM Satellite Radio. Replaced bad alternator and 175a fusible link...much fun!
Intake plenum---GONE!!!!
My car growls louder than yours.
If I can't buy it, I'll build it...Trust Me!!!!