I a have a 2010 RX 350 with about 9,000 miles. The engine has developed loud valve and tappet (I think) noise after about 5,000 miles. I am working with Lexus to find a resolution to this problem and have worked with the local service manager, the actual technician and a regional specialist. So far they have given me an answer that I don't think I or other RX350 users are going to like; which is "that's the way the engine sounds". Interestingly, I test drove a loaner with 700 miles (no noise) and a loaner with 12,000 miles (same bothersome noise as my auto). This could be a really big problem for Lexus in that owners buy their product for comfort, power and a quiet ride.