If its 18 PSI on low, dont turn it up - otherwise your rs ownership stage of your life will come to an expensive end, 2 Stage boost controllers usually half the PSI, so if your running 18 psi on low, high will be 36 psi which i dont think works out

for example, my low boost is 13 psi, and my high is 26 - 27, but sometimes on a nice cold morning or night, it will boost 30 psi - now thats fun !