My recently leased 2008 528i Sport has not idled smoothly since day one. When dropping down to idle speed quickly, the steering wheel and driver's seat would shudder. The dealer at first found no faults and did nothing at my first visit. On the second visit, the idle speed was increased to above spec, which only resulted in a constantly vibrating steering wheel at idle- whether cold or hot, whether in drive or neutral. The engine also feels less than silky smooth at low rpm's. Now I am told that there is a TSB involving new engine exhaust brackets to solve the rough idle problem. Is anyone else experiencing this problem or the TSB? Are there any other potential causes that the dealer may not be addressing? -- BTW: the three loaner cars I have had (328, 538) did not display this annoying engine/steering wheel/ driver's seat vibration. Help!