I just called and talked with the FASS techs the other day. Got in touch with someone on my first call and were very helpful.
They said if you have a 150 series FASS and want to bump up the pressure you need to remove the fitting on the fuel filter side of the FASS (at the base, not the top portion with the motor mount. Remove the fitting and behind it is a small spring and check ball, be sure not to lose it. Take the spring out and stretch it just a little and put it back in. Then bleed off the system and check your pressure. This should increase your pressure to your FASS.
Just remember you can always stretch it a little more, so go easy on it and only do a little at a time until you get your pressure where you want it. Hope this helps.
Also I asked if there was just a replacement spring to put in to increase pressure and I was told no, so just figured I would mention that in case you were thinking it would just be easier to put in a whole new spring like what I was thinking.