I just bought 2008 LS460 certified one. I noticed that I have the same probelm. I asked a local lesus dealer to check the engine and take care of the noise, and they said everything is fine. The noise still bothers me a lot. I have 2 other Lexus (ES300 and GX470) and know that the noise is not normal for Lexus. IF you have resoved the issue, please let us know.