Hello! I have the Isuzu Ascender 06 4.2 model. I've been having this problem where the gas cap light comes on after driving for more that 6 miles. The thing is that the gas cap is brand new! On top of that. After a few times that the light comes on, it triggers the check engine light with the gross exhaust leak code. Please help how to fix. My smog test is coming up. I'm in El Paso tx and they are tough here with that test.