[Daox]

Throttle position sensor.

What do you plan on using in addition to the EFIE? Just leaning out the mix will cause a increase in NOx emissions.

To solve the 2ndary O2 sensor you'd need another EFIE hooked up to it to get a consistant leaned out mixture. Maybe you could use the one EFIE to send out signal for both O2 sensors?

There are wideband solutions that do the same thing. Innovate has a simple setup (you need a laptop) for $200, and Zeitronix has one for just a bit more (230-240ish) than that with some very nice datalogging capabilities. Then, you also get the benefit of exactly monitoring your air/fuel ratio once it has left the narrowband sensor's operating range.