The tumble flaps have the appearance of throttle butterfly valves and the bearings supporting the throttle spindle may wear. Therefore, It may be the flaps themselves making the noise as they shift position on the "throttle spindle" and contact the sides of the intake ports.
Don't confuse the tumble flaps with the variable length intake mechanism fitted to the SVT.
Some detail here for you with pics if you follow all the embedded links:
2005 ST P2004 Help