I was pissed at my friends because they were being gay and didn't want to go out so my GF and I got in my car. IT had been sitting for a while maybe 2 hours. So I get in start it up wait a min or so. Drive off put it on high boost and tear as up the street so they could hear me LOL. The hole block for that matter. I got on the back road that goes behind their house and I did it again but this time a while. The windows were down no music. I am tearing *** down the street and hear a Zing Zingggg sound. I am like WTF ask my GF did you hear that? "No" Zingggggggg Zinggg Zinggg..... So i stop. Look at my AFC Knk Count 0.... What was that? I was running about 19 psi.... Very Conservative AFC settings.... I don't understand the ZING! Sounded like when you take a sword out of a holester. Is that ping? If so why didn't the AFC see it?