I think the air dam is to keep bugs off your undercarraige. At any speed we could be driving, I doubt it comes into play.
Just lifted my 4x4 wdith the daystar 2 1/2 leveling kit. Love it. Truck looks right. Only lifted it 2 inches though. Back is 40" and front is now 38 1/2. Like the rake that is left. Am now looking at the dam to get a little more clearance . Don't want to be ploying the sand when I go surf fishing.lol
2012 SLT 4x4; 5.7 Hemi: AirAid CAI; 2 1/2" Daystar leveling kit; Cabin AF installed; Black aluminum tool box; Front Receiver Hitch in near future.