To trick the computer into not knowing you’ve bypassed the catalytic converter in a setup with a post cat. Sensor you could try using an oxygen sensor spacer You could make your own or just buy one online See attached photo Offsetting the sensor back out of the exhaust flow will change its output just right I’ve had success using this on early 2000s beater cars for farm use after the catalytic converter collapsed internally and had to be removed to prevent back pressure on exhaust.
