Hard time accelerating but motor will rev high

[dguenthner]

After I filled fuel today my 2010 Impreza (non turbo 2.5i) would rev the redline but would not go over 45 up a large hill. I was able to get it up the hill finally and stopped. No cel's not running weird. I babied the car home (40 miles) was eventually able to get it up to 65 but it would drop the gear going up hills and rev high but wouldn't gain speed very well. I have an auto with the sports shifter. I tried the sports shifter. It did ok going from 4th to 3rd. But when I dropped it into 2nd I would rev high and almost sound like there was a a little gravel in the motor ( or it was the heat shields not sure). Took it for a spin when I got home and It seemed to struggle a little bit and run a higher rpm to get up to speed and then did the same thing when I floored it.

In the last 6 months I've changed fluids and spark plugs as well as changed the mass air flow sensor last year. I also recently changed out the rear piece of the exhaust that has the muffler and the exhaust manifold and front cat.