If you never run less than 14 psi go with the stiffer spring. As boost increases the back pressure does too and it pushes on the WG valve. With a 7 psi WG spring you are probably close to the limit before boost starts dropping at higher revs, unless you are on a large hot side, then maybe you can get a few more psi. I can hold 38 psi to redline with a 16 psi spring. With a 7 psi spring running 22psi, boost would start dropping around 6000 rpms and be 20 psi by 6500. I run a $15 regulator style controller (in both Z's) that runs pressure into the top of the WG, dead reliable. If it fails, then I'm at the WG spring setting.