I have this exact sound but in total opposite way. It happens when I try to accelerate under same conditions ie. driving for a while, engine warmed up, typically after 35-40mph and when I press the gas pedal down more, it goes away. So I sort of coast drive the Jeep, where I lightly push the pedal to gas, when the sound comes on, i let go, press gas pedal again, gain more speed, and drive it that way. What could it be?
I would check all the bolts around the throttle body,intakes and manifold. Make sure they are all torqued probably.