what he sead if the car is running perfect it wont need a cat at all but these motors are older burn alittle oil maybe alittle low on compresion the cats are saposed clean all that up and after market cats suck and wont hold up to less than ideal conditions i run a msd clone igition unit that makes multiple sparks under 3k makes for a nice complete burn and clean emitions but might not pass visual inspection i hide mine under the spare tire and i go to the smog only smog ref guys they atleast know there isht and the cleaner the oil the less burning it will afect the emisions so change it right before you smog it i.also.have a smog designated exaust system i through on for tests and then pull it off again and run my home made set up the rest of the time might be a way to go.for you have new cats made up that bolt in take them out after the test and you will have a nice fresh cat for your next smog