lamk

Does anybody notice a very faint hissing sound on accleration when you drive down a very quiet strech of road. I thought it was the usual A/C hiss but it is still there with the A/C turn off. It is not noticeable on the highway because it is easily masked by other noises. My RX330 is not involve in the exhaust manifold recall according to Lexus Canada. Any thoughts? The dealer said they can't hear it and just said the new engine sounds different from the old 3.0. Didn't have a chance to drive another RX330 for comparison.
Rx330 siver multipanel moonroof