A/F reading changed after MSD 2 Step installed

[henchmen3]

I installed a MSD 2 step this week and took the car for its 1st drive today. Noticed while at a red light the A/F gauge was at 16. Driving normal it was between 14.5-15.5. Use to bounce around 14.5 before the install. Car feels fine. Also added a can Torco octane booster ( would that matter ?). Thanks for any help