U want a spring pretty close to the boost u want to run mate, im going to run a 1 bar spring but run 1.4 bar through my AVCR, apparently its harder to control with the boost controller if your running a spring way off your highest boost setting, i wanted a lower pressured spring so i could run low boost in first and second but now il have to run atleast 1 bar, i was told this by Mike at TD :-)