Many people have had this problem; there was another big thread about it awhile ago, but no real solutions offered. I asked my dealer about it and he just trotted out the 'aftermarket suspension' and 'cracked undertray' card and waved his hands at me...
"I will tell you there is a big difference between driving money and driving blood, sweat and tears." - PorscheGuy79
"I got 328 loaner and was impressed with performance. It feels much faster than my 135i." - MOCKBA