I had mine professionally tuned…. Dude teaches Holley tuning classes… i had 18” after the collector…. I had that popping and LOVED IT! But the O2 sensor was going way lean…. I added about 4’ of straight pipe and some down turns right before the axle…. The O2 sensor now reads much better… but I still get pops. I still love it…. It’s just the engine brake sucking some O2 at the end of the pipe…. It’s fine, sounds amazing when I down shift or let off gas. To each their own I guess. Btw…. 11:1 ratio here.