Bobcat 753 Low hydraulic pressure

Hi everyone! I am working on my 753 and I can not figure out why the pressure can not go higher than 2000psi to the boom cylinder. Everything works fine , bucket lifts all the way up when its empty. If any weight in the bucket it wont lift. I just put in a new gear pump , still the same.I do not see any leaks. Just change all seals in the lifting and tilting cylinders. Any idea , suggestion ?

Bobcat 753 Low hydraulic pressure