sounds like something is wrong. also the efficiency goes up when the gun is broken in too... not down. my drone took almost 8 cases the doubled on efficiency. my vx with 12ms is in its break in stage and gets a good amount of pods out of a 68/45. you should leave the gun on 12ms until the situation is figured out. also bad paint will case terrible consistency.
As long as you don't need to up the pressure to keep the same velocity, you can't really break anything. If you do take it too low, you will just notice that your consistency suffers. Also, get some Viton o-rings for the valve, they last much longer.