^for that to happen you really really have to abuse the car, no DD will ever have them problem from normal driving. I have countless hours on my track car and never had a issue on my ap1 lol very few have ever reported this issue so I doubt he has it

 

intermittent mystery noises can be difficult. Try

branch stuck under the car
loose body work "flap" in front of tire (if the 2006 still had them)
loose under-tray
loose fender liner
loose anything bolted to the side sheet metal in the engine compartment
sway bar bushings
sway bar end links
steering tie rod end
lower ball joint
upper strut mount
all other suspension bushings

 

This is real. I had this happen, but it never made noise. But some reported a popping noise associated with it. Eventually mine got loose enough for the car to start steering itself as the suspension shifted. Undercoating tends to hide it in early stages.

However I wouldn't look there first unless your car has some specific history. As far as I know the only cause is repeated hard braking when using high grip competition tires. Autocross competition, where multiple maximum braking events occur in every run is where this was first reported. (Until recently, soft compound, nearly treadless, not recommended for street use tires were legal in autocross "Stock" categories.) This is a metal fatigue failure that requires many many repetitions under high load, a load that may not even be achievable with road tires.