E320 throttle lag (Update)
 

I took the vehicle to the dealer and they did a test drive and then gave me Dealer Technical Bulletin 50/01 (Simultaneous Application of Brake and Accelerator Pedal)
Sounds like my problem was caused by a bad driving habit. (Mine) Bulletin states that simultaneous application of the brake and accelerator pedal will result in the engine ECU returning the actuator to the idle position resulting in a 1-2 second delay until the actuator moves to the new accelerator pedal input postion. Guess this explains why the problem showed up in low speed driving and parking lots. At low speeds I tend to drive with my left foot on or near the brake, always prepared for some other driver to make a dumb move.

Thanks for all the inputs.