[mn box s]

I replaced my entire exhaust with S.S. duloboz and fabspeed. I need to get some software to get the car running correctly. Im throwing codes because my fabspeed test pipe 86ed my rear o2 sensors so now Im running two instead of four 02s I bought four new and installed only two due to the fact that there were only two bungs (on headers.) Obviously Im throwing CEL codes for o2. I should be able to get away running the front two only because they are (i believe) the ones that read the air/fuel mix? Im thinking of welding in two new bungs but I dont really want to. Also if I was to do that Id need some o2 extention wires I heard that mustang ones work??? What I really want to know is if a software upgrade (chip) you could program the two rears out? Please help, thank you! thank you!