Anyone know if the simtek ecu on my 2002 sti uses the first lambda sensor in the exhaust manifold?

 

from what I recall it only uses the rear o2 (one in the downpipe) for basic fuel adjustment. You have to fit your own aftermarket wideband if you want it do to the auto-tuning/closed loop fuel adjustments all the time. This is because the stock sensor reads in mA but aftermarket sensors all give a nice output in volts that the ECU can be calibrated for.