Help needed passing Emissions!

We still have to smog test vehicles '76 and newer here in Ca. I remember back when I had my repair shop that some smog equipment actually made more smog than if it was missing. A case in point was a late '60's Mustang with a 289 that came in the shop for a tuneup. The car ran perfect after the tuneup, and the emission specs were way below max allowed. The customer had to take it to a test only station to get a smog certificate. It failed the visual.....missing smog equipment. That particular year came in both a Ca. smog and non-Ca smog version, and the customer's car was the Ca version. No price limit on missing smog equipment, so, after spending hundreds of dollars rounding up all the smog gear (mainly the air pump, brackets, injection tubes, heat stove stuff, etc.) the cost of getting it installed and working, the smog specs went way up. We could barely get everything in specs at the same time and settings.....and it didn't run near as good either. It was totally ridiculous to make a great running engine that hardly polluted into one that didn't run near as good and polluted more, not to mention the extra cost to make it that way.