My power steering makes noise. It's directly tied to engine rpm, not steering force, but gets louder the more I'm using the power steering. For example, on a long highway trip it will quiet down and you don't hear it, but getting on the highway after a stretch of corners and it'll be louder than the engine. I took it into the dealer, first they said they couldn't hear any problem, then they said the noise was normal. Is this true?