I've owned my '73 S for just over a year. Although it was running fine (it NEVER backfired through the exhaust), I discovered that the RPM transducer/speed switch was not working. I took the switch out and ran the car for almost two months without the switch even installed. This had no effect on the car (still no backfiring). I bought a rebuilt switch from Otto's in Venice and the car now backfires--a lot. It regularly pops when upshifting and can backfire badly when accelerating out of a corner after coming in to it at higher RPMs. The situtation seems to be slightly better when I am very careful about keeping my foot off the accelerator, but it still spits unburned fuel out the exhaust even then. I had always understood that these were the symptoms of a bad RPM transducer, but the good speed switch seems to have had the opposite effect on my car. Any ideas? (I know the speed switch is good because the car "hunts" as it is supposed to when the micro switch is depressed with the idle held at 2K RPM).