Nitrous N-tercooler system

Hey thinking about getting this system. What do you think of it? and how does it work do you spray while your racing or right b4 your race and also i know very little about nitrous the cheapest system comes with a 5lb bottle how long would that last?? and it also says co2 is an option which would be better?

thanks for all the help guys :banghead:

my friends with STIs or other turbo cars say the systems are great with less problems then direct or fogger im pretty sure you can spray it when u want on the IC make sure ecu is ready and ok with the xtra power .co2 is good too