Nice set-up. I bet that is fun. If you've smoked the system with no leaks there probably aren't any. If it's a header tick you're hearing that kind of stuff comes with the territory of running headers. Sometimes that stuff is hit or miss if it's an issue or not. Only thing I think you could try is ceramic coating them or wrapping them in hopes that it provides additional sound deadening from the headers? I guess there is an offset chance there's a porous weld or small weld bit of steel bouncing around or causing a noise, but those type of QC issues are slim with Kooks from my experience.
I'm a bit surprised it's still loud and obnoxious with the OEM resonator still place. I don't have headers or anything; But I got my hands on a Corsa 3.5" in/out muffler from their #14866 kit for the 6.2 Silverado/Sierra's and had that welded in, flapper removed, left OEM resonator in place and the sound/tone level is perfect. Not too obnoxious on cold start, but you know somethings there, great sound at WOT, and zero drone ever.
I think the Corsa Sport exhaust kits by themselves installed on the Tahoe/Yukon/Escalade are almost too loud on the cold start and at WOT. I never wanted to go that route anyway because their kit for the K2XX SUV's is still 3" and the OEM piping is 3.5" on the 6.2L L86 models.
Always got my eye out for a lightly used Corsa #14866 kit for 6.2 Silverado/Sierra's due to it still being a 3.5" system. I'm confident it would take minimal modifications from a muffler shop to fit our K2XX SUV's easily and add a 3.5" Vibrant resonator in the back around where the OEM one is located and it'd be perfect sound/tone, wouldn't sacrifice performance with the mandrel bent 3.5" system, and it'd all be stainless.
