2006 X5 4.4 vibration/surge while in park or in gear???

[salnteresa]

When at a stop there seems to be a rythmic pulsation/vibration to varying degree coming from the engine. The tach doesn't move but it can actually get quite annoying. It seems to happen both in park and at a stop. With and w/out heat on. The engine is fully warmed up. Once I begin driving it goes away and returns at any stop. The dealer says there are no faults being thrown and he can not replicate. I am insisting there is something wrong because a BMW should not be doing this. The tech suggest they do a injector flush/clean. Because of carbon build up and cheap gas. I told him i only run premium gas. I had them do it which cost me $150.00. The truck still surges. I only have 40K on this truck and it's got us stumped. Any thoughts before i take it back to the deal???