So I've been considering removal, bypass, or emptying of my cats for performance and fuel economy reasons. Does anyone have an idea of what kind of MPG improvement this might yield due to the reduced exhaust restriction in the system? Also, how will the computer handle it given that the upstream and downstream O2 sensors will read about the same? Will it throw idiot lights? Would I need to disable my downstream O2 sensors with my handheld programmer? Advice wanted. I'm weighing the benefits versus the known drawbacks (among which I include the various fines). I'm just doing my homework for the time being so that I can make an informed decision. Surreal P.S. Yes, I know I won't pass emissions tests if I do anything other than a bypass (a la electric cutouts). I'm not worried about that.