DiRT 3

Since It's jam session it can be boosted easily, just set up a race with a partner and exchange wins, you can combine this with "New Wheels" if you want by just varying the event type and car selection so you work your way through all 5 cars. If doing normally just refer to "New Wheels" again for the event/class you need to look for when searching so you will be able to use one of the cars. Win 5 races with any combination of the 5 cars and the trophy is yours.