Ah rattles... I have had 5 Lexus including the ES which I have now (and is my second) and every single one has rattled or made some kind of buzz noise. Take the current one, somewhat intermittent buzzing from headlining, seatbelt adjuster, somewhere towards the front of the dash (who knows where), somewhere over the passenger side (might be seatbelt related) and somewhere in the driver's door... Over a smooth road the car is silent but as soon as the road surface gets rough, and most are, then at least one of them appears... or doesn't. It seems a bit fruitless trying to get to the dealer and not be able to replicate it consistently so I haven't bothered so far...