As per AEM, you want the wideband o2 sensor 36" downstream from the turbo. Though I'm supercharged, I just had mine welded into the downpipe on the headers.

If the sensor isn't hooked up, the gauge will show 14.7 all the time.

With the sensor hooked up, you should be between 10.5-16.0 or so all the time. Cold idle with my 42's shows around 10.5, and gradually warms up to a 14.5-15.0. Cruising is similar around 13.5-15.0. WOT drops down to 11.0ish.