If you don't already have one, check any RODI
vendor and they'll have in-line pressure guages that you can add in for pretty cheap. Basically, you just cut the source water line, and the guage comes with 2 quick fittings. This way you can check your water pressure, and then determine if you really need a booster pump.
I have the same issue. 100gpd RODI
filter, I can only produce about 1/3 of what it's rated for because my water pressure is only 30psi.