dont have a zetec but if you get that code it is most likely true, although before i replaced the two upper o2 sensors i was getting a code for system to lean on bank 2, now i get that both banks are to rich (from the 19lb injectors im running) and another code buts thats about my mil eliminator

98.5 Black SE ATX S&B filter, SVT MAF, optimized SVT TB, mesh grille, removed orange reflectors, painted rear reflector, gutted pre-cats, optimized SVT LIM, 19lb injectors, resonator removed cant afford an svt but lookin for 1 in nc