Any chance there is an agitation line that needs to be closed some to build more pressure to the booms?  Also in my experience 40 psi is about what a hydraulic drive pump will make if you hook the hoses up wrong and it's running backwards.

I usually tried to run my AI tips at 50+ psi unless it was really windy, I really felt like the Turbo Tee induction tips worked best in the 60-80 psi range and in drilled beans sometimes I would run them at 90+ psi, I figured if I could see the crop leaves moving under the tips then I was getting some chemical through the crop canopy.