has anybody used one of these Vortex untis? any problems arise? the reason i ask is that i had one on the Hotrod m944. then my gas tank started to leak. it could have been a coincidence. lot's of older monsters have tank leaks. DNA replaced my tank this summer. it's all new and perfect now. i really like the look and functionality of these caps but don't want another leaker. one thing i noticed when i had this type of cap on the old tank was an escape of air when i opened the tank to refuel. the cap seems to be vented. what would cause this?