I chased a similar problem with my 07 Silverado 2500HD. With cam, headers and tvs2300.
Latter found that the main bearings especially the thrust bearing was trashed. Only had 28,000 miles. For peace of mind, please check the oil, and hopefully you are using a magnet somewhere on the drain plug or filter. I use BOTH now. Had to rebuild the motor.
Not saying that's your problem. But we chased a mystery knock for too long.
GL, Tom