I purchased this iPod adapterat Best Buy ($100) that allows me to listen to it through the radio..it plugs into cigarette lighter...alot cheaper than the $600 + BMW install. Anyway, when the engine is off the iPod adapter is still on. I've been taking it out after I park the car and at night out so it doesn't drain my battery. I was told by the guy at Best Buy that the amount of battery drain is miniscule (if the iPod is not connected). Is this true? If so then it shouldn't be a big deal leaving it in, except if I'm going to not use the car for several days.