Err, I thought part of the Bazzaz AFM install was to disconnect the stock 02 sensors, and then you just screw the Bazzaz 02 sensor into either of the stock bungs in the header. Why do you think it should be downstream from the cat?
BTW, I don't have mine yet, probably arrives next week some time. Will let you know what I do.
I went the DanMoto cat delete route (cheapskate, saving $'s for trackdays, so sue me