Your upper control arms are topping out and hitting the stops (metal on metal) as you come off a bump and the suspension extends. Once you go past about a 2" level in the front this starts happeng, depending on the severity of the bump.Did you do a before and after measurement to determine yur actual lift? My 2" Tuff Country gave me an actual 2.5" and I occasionally get a pop when dropping off a curb a little too fast or something similar. Not that I EVER do such a thing...........
2005 F150 5.4 FX4
2011 F350 CC 4x4 6.7 PSD