I've noticed that my new 2010 Prius engine seems to be working WAY too hard trying to accelerate while going up a reasonably steep grade. I have to basically floor it to get it to increase in speed at all, and it sounds like it's revving at really big RPMs. Is this normal behavior? Once it gets going at a particular speed it seems to be able to hold it fairly well, but this is worrying me. The battery is at more than 1/2 charge while this is occurring, so it's not related to charge issues. Any help/feedback would be appreciated.