pcs

so im looking in to getting a cat back for my truck but i also want to ask if anyone has modded their y-pipe or installed and off road y-pipe. i looked at the stock y-pipe and the last 2 cats dont have an o2 sensor behind them so im assuming that the computer will not know if they are there or not. i would just rather get a pre fabbed y-pipe but i dont mind chopping my up either. has anyone else done this? i also read that o2 sensor simulators do not work on 05 and later models, is this true? anyways, any inputs will be appreciated.