Is it bad to drive with a semi clogged main cat?
 

Just wondering what this might affect,well besides the power loss,but is there any damage by doing this,i'm babying the car ,and trying to stay off the boost,just wondering what all that back pressure might do to the engine?

I wonder why you think your cat is clogged.......and assuming you don't have a downpipe, which one is it?
About the only way to know if your cat is "semi clogged" is to take it to be tested. If it is restricted you will be causing potentially severe overheating problems and it will likewise toast your engine. Midas will check it for about $10.00 but don't take your eyes of the monkeys while they have your car, and be very skeptical if they tell you that a new one is in order.......I recently had a clogged main cat on my 88 Chevy truck at 95,000 miles.
They (Midas) told me it was clogged, so I had them cut it off and hand it to me - sure enough you could hear all the junk inside rattling around, it sounded like it was full of sand. When I asked what a new one would cost they quoted me $2,300.00 for the repair. When I told the shop manager that I was an FAA Certified Repair Technician and that he was a lying, cheating bastard he threw me out (with converter in hand) I called the Midas district manager and he directed me to another nearby Midas shop for the repair. Cost: $160.00 for a generic converter plus $80.00 in labor, and I got a certificate for a free oil change. It passed emissions with flying colors.