ah dude.. you must be having a laugh.
"that doesn't compute" - did you watch the video 
drill holes in your tank.. wtf??
he doesn't have a turbo or supercharger.
the rocket tank has 2 vent pipes, one with a rollover valve.
i'm no doctor but i'd say the port that's blocked in his tank by the gas cap gasket is the one with the rollover valve on it (there to let vapour/positive pressure out (but not fuel if tipped over)).
petrol flashpoint is like -45° or something, so it's throwing off vapour in any weather.
get a jerry can and a couple gallons, seal the lid. give it a day or two then open it - phoooosh there's positive pressure pushing it's way out 
