Why?? I have been running triple throttle bodies with a narrow band for a year now -- car pulls 250 @ the flywheel and a 13.7 quarter. 99% of the time the sensor is out and unplugged, as the ECU holds true to the map then whats going to make your ratio go out? Running your ECU in closed loop will never yeild the results that direct map will, Get it dyno mapped and leave it.

The local chassis dynos are only good for full throttle pulls. Since this car is used for SCCA Solo II racing I also need good part throttle and transistion power. The O2 sensor will be used to develop the map, then I can find tune it on the dyno for full throttle applications.

after reading this I really want to get an analyzer myself

http://www.triumphclub.co.nz/su_carbs.html

But I wandered for tuning the su's if it would be better to find a 4 gas analyzer for more accurate testing across the complete power band.

WOW, after reading the link I definately want to do this. Thanks for the read.