That would be annoying! I've had my '09 for about 10 days now and I haven't noticed any whistle on acceleration.I did a little poking around on google and really couldn't come up with anything other than some people that had this problem with other vehicles were able to get rid of it by using a different type of air filter (i.e k&n). Makes sense if you think about it..... If the whistle is coming from the air duct, making a small change in flow could get rid of it (...or make it worse...). If it's at the throttle body I'm not sure if using a different filter would have any effect.
I'll keep listening.
