Show a picture of your cap and the drilled hole.
This is te cap that's been on my truck for several years. Worked fine until all the gas tank nonsense and now causes a vacuum to be created in tank.
That cap looks different than the ones I have purchased. The plastic in mine is blue without holes.
The ones I had trouble with also caused a vacuum in the tank. I would hear a giant sucking sound when I removed the cap, especially when the fuel level was low. I do not know if they allowed excess fumes to escape. In my opinion, they are supposed to vent, and not retain a vacuum.
