Here is the real answer. I've been racing Z's for 20 years, all different build types. Get a helmet with a fresh air vent. It's a foolproof method. I always have used the fuel rail cooler fan from the fuel injected ZX because it blows just right and doesn't use gobs of power. There are many brands of this. I prefer the helmet with the top air inlet as it doesn't bind and distract you when you turn your head back and forth.
You can chase fume leaks until you're red faced, literally. This is the only thing I have depended on. We run 110 octane leaded fuel. Believe me, you know for a day or two that you were on the fumes.