I got the same car like yours in the end of March this year but is black, after three week i got the same problem here(the noise), i went to the service at the first time they tell me it is normal, then i move to the dealer, the sales drove back right a way to the service, bacause he feels the same, lexus cars should not have that noise, the service guys saw i am very not happy with my car then they try to fix it, after they fixed, the noise reduced 90%, but i feel my car runs not normal, i don't know how to say here, sorry about my english, the car looks very good but.........
