The fuel pump relay on the 2008+ Evolution X is a common trouble area. The most common symptom of a bad relay is the car running lean. Typically, the "black" relay is bad and should be replaced with the blue relay. The relay is located in the engine bay fuse box as seen below. The part number from Mitsubishi is 8627A024.
**Note: Newer model EVO X vehicles (Final Edition) may already have an updated fuel pump relay from the factory. These are generally a Panasonic part number.
Here, you can see the contacts on the relay are burnt out. Therefore, the relay can't make a solid connection, so it never switches to high speed mode and the vehicle runs lean.