Bobcat T590

Hello everyone, my boss and I have been having an issue with our Bobcat t-590. Basically the arms do not want to lift at a normal fast pace compared to our other equipment. We have battling this issue for a long time now and I spent my entire day tearing into the pump and replacing seals and checking o-rings and it’s still having the same issue. It will operate at normal when the tilt pedal is used at the same time as the lift pedal. I am hoping that maybe has had this issue before And has fixed this problem. Your help will be greatly appreciated.