My 98' doesn't seem to be the quitest car I have been in that's for sure. I don't think that the road noise is that bad unless you are on a real rough road (that's all we have here in MI), but other than that all I can think of is your tire noise in general. I recently bought Bridgestone Potenza RE730 tires for my street tires on my Mustang and they have this "noise cancelation tread configuration" that in my own opinion makes a real strange and kinda' loud hissing noise that I have never heard from the rear of my car before... and it is due to the tires (although I love the tires). It could just be a general charecteristic of your tires to be honest with you.
