I have the ro man 200 using there booster pump. i have set the pump to about 95 psi (not sure if recommended as pump info states output at 50 - 80 psi) ro man says there systems are tested to 100psi. Using this pressure i have found that my TDS is about 360 in and my out before DI is 001. The only draw back is that the higher the pressure the lower the output flow rate.
Ro man recommends pump before pre filters.
I did not know about the timer being required, but it states in the instructions that the pump is for "house hold Ro's only" so i don't expect they would normally run for very long for household use.