the apexi learns your speed through your speed sensor and then adjusts the boost curve Accordingly i can still have 30psi in first gear but later in the rev range, so even if i use nitrous the boost wont come in as hard as normal. in order for the turbo smart controller to give different boost per gear there is a green and yellow wire which have to be earthed out so you can go from sp1 through to sp3, but you have to do this either by a switch or some sort of Solenoid Mechanism