the more poundage the spring the more boose it will hold,im running cozzy managment on mine after 15psi the ecu dosnt know wot to do so i had to change my spring to no10 to get it to boost up to 16 psi and hold at 15,the one that was in was shooting up to 25 psi and dint like it.basicaly its a softer spring in it now.