2010 5.3 Silverado, w/ 6 speed and AFM. ~20,000MILES

The truck drives smooth and no ticking in general. But when it drops to its lower gears, near 1000-1200rpms, and you apply light throttle/load, you can hear some ticking just for a second. Usually then the tranny downshifts, rpms rise, and it goes away.

I have checked the exhaust, no problems there.

I have checked the lifters/valves at dealership, no problems there. This is not the typical lifter tick at startup!

I have been told it could be sound, resonating through the exhaust as the engine lugs....or it could even be the fuel injectors firing? Anyone confirm this? Anyone with the same truck hear this on the drivers side?

Your help is greatly appreciate. Thanks