anyone had any problem with a check engine light coming on after installing a high flow cat. Mine comes up catalatic converter not functioning properly. So i bought an O2 simulator its supposed to give a proper code to the engine so you can punch out your cat without it showing up bad on your computer. and i'm positive its hooked up correctly and now it comes up rear O2 sensor not functioning properly. Any Ideas?

 

pull the sensor back out and inspect it, you might have wacked it installing it back in. also if there was any type of crust on the old one when it was reinstalled.