readings on ngk and dynojet wideband.

I have my ngk wideband on my driver side exhaust, where my catalyst use to be. I strap it on my friends dynojet and didn't have another o2 bung for the dynojet wideband. So since the car it's on open loop I took of the passenger front o2 and place the dynojet wideband sensor. Now they both read different 1 whole point of, My ngk was reading 13:1 and the dynojet was reading 12:1
Should it be because it's on the passenger side? I have always put my ngk on all my cars in the driver side and have tune them and never had a problem. What they reading different?:confused: