more of a wrong GPM pump.. vs pressure. 2500 psi is a common ag pressure.
He might have had an 8-12 gpm pump before and now has a 16-20 gpm pump.
the owner can reduce rpms and thus reduce flow, and try to feather the spool a bit more...
One thing i'd check is to make sur ethe valve is rated for the flow from the pump. if they are not a good match.. the pump will not like it as much.. however it sounds like the valve is NOT an issue. you can also get restrictor orifices and even 1-way restrictors that are full open in the other direction.. just be carefull with restrictors..