I keep hearing this about the S4 but do not know much about it. Is this an expensive SERVICE that needs to be performed once the part/parts wear out? Or is this the expensive repair when the timing chain tensioner whatever BREAKS? Or is it a service that needs to be performed so something BIG doesn't need to be replaced? Is this generally the most expensive issue the B6 S4 encounters and how much? I'm hearing figures of $5,000+ Can someone tell me more about this and the costs? Are there bigger things to worry about regarding the S4?