Well, if the eccentric sensor is the same as the V8, it's an over $500 sensor. Not exactly a "preventative maintenance" item. They are malfunction prone but it could last a good long time too. Might consider just doing all the gaskets and seals and keep your fingers crossed on the sensor.

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2007 E70 X5 4.8i Sport Package
8x,xxx Miles
"My Precious" (Smeagol voice)