strange cabin noise.
Ok another thing that comes to mind is under the car, i believe somewhere around the middle of the exhaust, there is a heat shield near it. Some people reported their exhaust hitting/scraping it at high speeds. May wanna get it on a lift and make sure the exhaust is not close to anything or making contact. Also, make sure there isn't alot of play (as in make sure the piping is secured with the hangars/brackets. And make sure all of the bolts are tight.