If you want to save cash on fuel, you HAVE to get an ecotek valve... it's great for the environment, saves you loads of cash and you can tell girls about how nice you are to the environment!
I'm sure that'll work lol, I may try it some day...
http://www.directcarparts.co.uk/ecotek.htm
If you're not in the UK, hard luck (nah, just kidding! google 'ecotek valve' and you'll get loads of results
)
Alex