O2 sensors go before and after the 1st muffler off the turbo. I think you meant the secondary O2 sensors, the pre's are what the ECU goes by for AFR and the secondaries are turned off (or recalibrated to a set value) to avoid the CE light.

Markski, did that MAF work out ok for ya?

 

Are you saying there IS as tuner that turns off the pre cat 02's????
That is very scary if its true...

 

+1, isn't the first O2 the wideband (5-wire)?