A respected tech on another site once said you're wasting your time with pressure bleeders unless you can get at least 30 psi out of them. Professional units can go that high easily. The instructions with my unit said to set it to 15 psi. I never felt that I got as firm a petal with this unit as I did with my foot.

Again, my 2 cents. I suppose not all bleeders are created equal.