For anyone interested in using nitrous oxide you should definately visit this site:

www.nitrous.info

It talks you through building your own nitrous system and getting the most out of it. Ive read through it for the 400th time and i am now collecting the parts required to build my own system. I found it really well set out, and he claims you can build a system for about £40, which has go to be good! However, some of the places hes cut corners to save money seem a bit dangerous to me, like using fire extinguishers found in skips that have failed their pressure test for a nitrous bottle, and using bits from a biro pen to name a few.
Anyway, theres some other stuff on the website about power tuning electric wheelchairs etc so its well worth a peek.