I have a catco high flow cat with a new oxygen sensor strapped outside of the cat with the old one pluging the cat,i was wondering if this was ok and if it woulc causemine engine to run boggy and stuff,ya know typical bad oxygen sensor stuff???the new one is hooked up outside becasue the ECU would throw a CEL cause of the higher flow!it is a 2000 civic EX

*P.S. when my gas tank goes close to empty,it seems like it is harder on my car to turn over,could this be something crapping out,like the FPR, fuel pump, or starter?