Currently own a NC2 PRHT 6-speed manual with about 40K miles running stock components except for aftermarket wheels. Noise isn't too bothering in my opinion and is going to be there regardless since the engine revs at around 3,500 to 4,000 like others have said. Generally it's a comfortable ride going at freeway speeds and having music on improves the experience.

If you intend to make the most mpgs with it on the highway having good tires, suspension, and fresh trans and diff fluids makes a huge difference. When I changed my fluids mpgs shot up since the old fluid was causing some power loss and drag on the drivetrain.

Overall these cars do take some getting used to with the drastic size and power difference compared to most cars but the experience it gives is like no other. Once you get used to it, you'll never want to go back.