While I have no room to say i have a great deal of expertise in this area I can say this, I have hit my headers/cross-over with a wrench and lightly tapped it with a hammer to try and see some KR (I was worried at the time my knock sensor had crapped out on me) and I was unable to get ANY knock. I also know for a fact that my O2 sensor is FIRMLY hitting my fire-wall (I have been meaning to have it moved to the cross-over just havn't gotten around to it) and I still see no/little knock at the shifts. Not saying anyone is right or wrong here.. Just adding my 2 cents.