not as described and car finance

Hi i bought on car on 2/4/2013 from a second hand car garage, and got finance on the car, the car was advertised as a 2007 on a 56 plate, now i have found out there were many changes on my model from 2006 which came as standard better leather seats etc,but most important the engine received some major changes, now since i have owned the car 3 weeks and had a service carried out and have found i have the older spec mode pre 06, with older engine and trim etc, i bought the car as it was the newest i could get and i am also in the higher tax bracket, seeing as the car is about 2 years older than i thought, is there any options for me to hand it back, as the way i see it if someone was to buy a brand new car and it turned out to be a 2 years old suerley that would be a problem
Any advice would be great thanks