what happens is.....

it massively retards the ignition to such a degree and ads extra fuel to an open chamber so when the plug fires the explosion goes out of the chamber and past the exhaust valve which is open at this time as its on the exhaust stroke....and the burning gasses blow past the turbo and keep it spining.....

its not quite that simple but its the basic...

speak to Karl Norris of NMS or Stu at MSD. they will help you