Dont know if anyone else has this problem or if it's common with the 05-09 stangs but mine seemed very noisy at highway speeds.What i did was to spray the rear wheels wells with that black undercoating can each side .and i got some anti fatigue mats at harbor freight and cut them to fit underneath the seats and back floors and also put then in the truck where the spare tire is. took on the highway and it made a big difference in the road noise mostly what i hear now is from the tires but it's much better.So if anyone else has this problem give this a shot .

 

thanks for the info. Did you spray any of that stuff under the floor boards?

 

No i didn't but that's a good idea also

 

Good idea ,thanks for the info. Noise in general is a problem with my exhaust as well. Ive got some serious sound deadening stuff on the way