Loosing speed going uphill and revs at 3500 rpm+

darsben1 wrote:
did you try downshifting?

He was doing 4000 RPM. Not sure down shifting is an option.

You may be maxed out on power but it doesn't hurt to check the things others have suggested. I fit has more than 50K miles on it, I would swap out the 02 sensors as well. They may work good enough for the computer to not turn on a light but they get lazy and rob power and fuel efficiency long before throwing codes.
For domestic products, they are usually very cheap and as easy to change as a spark plug.