the nitrous switch allows you to Add or subtract fuel and timing etc.. as a percentage of what your regular map was. You could add more boost, but it would be setup via the original map first and then have a + or - of fuel or timing depending on what type of setup your doing with the 'nitrous' map!

 

its a tad misleading as its still the same base map, just a percentage is added to it. My tuner said it works for Meth or Nitrous applications but wasn't the best idea for a race gas tune