1997 base wont pass inspection
 

Just bought a 1997 camaro base that isn't passing inspection currently...I'm not entirely sure what the codes were that it wasn't passing, but the mechanic said that the car wasn't showing loads put on the engine by the computer. Any tips or ideals about the problem?
We did manage to get 1 of the 4 codes to go through after about 15 minutes of driving the car, but the other 3 didn't come on after 3 more runs down the road. I think the one that went through was the catalyst, if thats of any help.
Thanks,