They are used for fuel cut, over 0.80-0.85 is when you get fuel cut.....When doing such mods i.e decat,mani,exhaust,air filter boost will creep over the set ammount and some times over 0.85 thats when the EM light will come on and it will feel as if you hit a wall or something?. the way to eliminate creep is to port the wastegate to a certain ammount.......my turbo knowledge is weak mabe some1 could help scooby out a little more?