Water pressure is reduced with a new forward bowl set.

[PRJSyd]

Hi All, I have replaced my existing Shaw and Mason chrome set with the Shaw and Mason forward bowl spindles/ Handles. I have kept the same tap or the water dispensing unit. The water pressure has reduced after I made the changes. I installed the original spindle back but same low pressure. If I remove the tap the water from the direct point comes at a very high pressure. If I try to open the spindle directly still the water pressure is fine. Please help.