YoungDiesel

Recently I was under the truck and behind my new exhaust(dual 27" glass packs, no cats) and I noticed a ~.5" pipe that had a nasty opening on it. It was putting out exhaust as well. I was wondering if anybody could identify this before I get home as I looked at it in the dark and didn't have much time. It's equipped with an EFI 300 6 BTW.