I read and have heard some of the direct injection engines from BMW (335i)are having some issues regarding carbon building on the intake valves and other components. Is this a common problem among all direct injection engines? My Audi RS 4 is sort of notorious for this issue and the apparent removal of the intake manifold and subsequent cleaning if not done under warranty is quite laborious and therefore expensive. Im contemplating another car,possibly 335i sedan or an A3 both direct injection but am a bit concerned about the long term reliability and service issues with this technology. Is direct injection something to shy away from totally or just with these two automakers?