obd2 code P0420 Bank one disappears at 60+mph. mpg=10 why?

What is your question?

Scan tool says with engine warmed FF Fuel System Closed Loop Calculated load 16.8% Coolant Temp 206F STFT Bank 1 0.0% LTFT Bank 15.4% Intake Manifold Press 15,0 in.hg Eng RPM 1504 Veh speed 36 MPH If the bank 1 sensor is causing a richer F/A mixture should that trigger FUE code? Will check for check 4 intake manifold issues too. How would u proceed given this infomation.