i had to use the spring. i fitted everything, chips circuit board, plugs fpr. then turned the actuator right down. i then put it in position 5 and started to wind the boost up by the actuator. got to a certain ponit and it wouldnt go anymore. fitted that spring and all is well, gonna get the guy who tunes it to set the boost properly.
like james said, i would have had to really preload the actuator to get that amount of boost.
do not try the kit without fittng the fpr first!!!!!