Mines doing exactly the same. It did it at the start of the year, EGR valve subsequently failed in June on the M6! Lexus did it under warranty as it had a valve July 2009, and guess what it's doing it intermittently again now. Car's done around 4000 miles since the EGR valve done!!! Got a service due v.soon so will be mentioning it again.
Drive's perfectly well but cant help thinking that anytime now the VSC's gonna light up and into limp mode.
Does your car have a miss fire, mine is getting worse tonight feels like the power is strugerling.