Originally Posted by 05RollaXRS

Believe it or not, this is more than likely your windshield seal. There is wind leak that goes through the windshield that results in howling/whistling type noise at highway speeds especially if you go around or over 100 mph. It is fairly common with Toyotas (and possibly some Lexus' too). My Toyota had it brand new while getting close to or over 100 mph when I got it back in 2004 and it took a long time to figure out. Initially, I thought it was the moon roof and Toyota refused to replicate the issue since it was beyond legal speeds. Eventually, I had a windshield crack and had to get the windshield replaced. It never occurred again after that.