Silly question, there is a filter on the filler neck. It seems to be leaking, if I put my finger over the end and let go it makes the car try to die. It appears to be leaking under pressure to. This is the only leak I can find in the system. It puffs as the car runs and you can physically feel air coming out of it. My question, is this supposed to do this, or is this my problem? I can post a picture of it, but f need be.