Carb'ed vehicles usually need to run like crap to pass those dam tests. I had a 79 F-150 with a 400 and a 79 Capri with a 302. I had to adjust them so much, they backfired, idled like crap and would diesel when I shut them off, but they passed the smog test. I had a removable cat on the capri too. I had header collector flanges on the pipes and on the cat and straight pipe that replaced it.