4040's like good pressure. They're so much more efficient with it. Just because you can run them unboosted doesn't mean you should. You'll get a longer life from the membrane and a lower product tds. Well, I do anyway. Considering how much people spend on vans, hot systems, extreme poles, electric reels etc. a decent booster pump often gets overlooked. It's a worthy investment IMO if you use a 4040 ro.