There's a evap purge control solenoid. If your looking at the engine its on the left side behind the alternator . It is bolted to the front of the intake manifold. I would check it and make sure all the connections are good no broken or loose hoses. You may want to also take a look around your charcoal canister. Its a black box behind the (right?) rear wheel. Check connections on that as well. Im not sayin those are your problems but, they are in the evap system and easy to check.
06' wrx tr