Originally Posted by J08M3
no software is necessary for secondary cat delete since o2 senosors are only on primary cats. Make sure to leave the resonators and you will have no drone or rasp sound. just straight pipe is all that's necessary as replacement since resonators already exist farther back from factory.
I deleted my 2nd cats AND resonators and there is ZERO drone. It's really not all that raspy either...only when the exhaust is cold and you rev the engine. Other than that it sounds more like a stock M5/M6.