What affects knock? (what makes a car knock)

[DoughtCom]

I know with Evo's their knock sensor is super sensitive and you get phantom knock or whatever it's called. I get knock even after a DB Tune, and I've read it's from my downpipe gently tapping the cross member bar.

I would look into your downpipe if you think your tune is pretty strong. I don't know about 1G's or your knock sensor but I know that's what's causing my problems, the Evo knock sensor is more sensitive than a teenage girl on her period.