This is the one I've been looking at. Would you say its reasonably loud inside on highway?
I don't think so, but I'm probably not the one to properly answer the question because I've also got a ProCharger, and that's the noise that I hear more on the highway. The exhaust I feel like I hear loudest at at start-up, but from there, not an issue at all.
That's start-up....personally thought I'd suspect if you just had the exhaust it would be noticeable, but not extreme.