1994 Chevy S-10 Failed smog what's wrong

First thing to do is if your check engine light is not on, then replace your fuel/air and oil filters and change your oil. Then drive teh vehicle on the exspressway about 10-15 miles or so. Or a road like it. Then while it is still warm, take it to get it tested and it probably will pass. If it doesn't pass then, take it to a pro so he can check as to why. If your cat was going bad the truck would probably not have any power and drive like the exaust is plugged.