[FC] FC Gas Cap Revisited

[scwilson8126 at wowway.com]

The new FC chrome gas cap I bought works great except for one small problem. 

  

If you remember my earlier posts, I was asking about the pressure build-up even though it is a "vented" gas cap.  Several of you said that the venting lets air in, but not out. 

  

Problem is, I have a small  hole  somewhere in the tank and the pressure is forcing the gas out on to my driveway.  Didn't have this problem with the old loose gas cap. 

  

I know the long-term fix is to repair the gas tank.  Can I drill a venting hole in the cap (maybe into the small hole in the center of the inside of the cap), or maybe at the top of the filler neck?  Maybe remove the rubber gasket?  I'd like to somehow use the new cap instead of going back to the old one. 

  

While I'm at it, does anyone have a reccomendation for removing gas/oil stains from cement?   I've tried Purple Power, several driveway cleaners, comet, bleach, powerwashing & etc., but the stain is still there.