[Eugene at Pelican Parts]

On 80s model SCs, oxygen sensors were sort of added on to an already (relatively) clean burning motor. During this period, as emissions regulations became more stringent, the O2 sensor system was piggy-backed onto the 3-liter motor in order to compensate. The device acted to lean (or continuously adjust) the mixture during idle and low RPM operation but was a somewhat archaic means of doing so. With CIS, removal of the O2 sensor will not harm anything and may even smooth out the low RPM operation of the motor, assuming the mixture is adjusted properly. Keep in mind that fuel consumption will increase slightly if the O2 system is disabled. The catalytic converter's lifespan may also shorten.

During emissions testing, it is obviously preferable to have all emissions equipment present and functioning properly to ensure the best test results. After you have passed, you may pull the plug again and adjust the mixture accordingly if you so desire.

The tunability of CIS is due to its simple method of operation (concerning half a million tiny little parts). Contrarily, it is important to note that the converse applies to Motronic systems; where every subsystem plays an integral role in the overall performance of the motor... I digress. Basically, the O2 sensor paired with CIS is not necessary except if you're environmentally conscious... which contradicts the desire to enjoy practically any sports car.

Ed, if the O2 is no longer in the cat, I somehow doubt it's still anywhere within the vehicle. To me, I would still not rule out this one. Use it as a negotiation point to lower the price a notch or two more. Good luck with the search.