Syncro LHD T25 Power steering /pump/rack

[syncro4us]

Im after a power steering pump as I think mine is not outputting enough and the steering is getting heavy. There are no leaks from the system.
Any suggestions
I have put new seals and filter in the old pump which improved it for a bit but its back where it started and too heavy to drive long distances. There are signs it overheated as the oil smelt so I wondered if the releaf valve had lost its temper and was opening early. Unfortunately the spring is held in by a fixed metal diaphram different to the exploded Diag in the Bentley Manual so I couldnt get it out.
The vanes inside still looked good though with microscopic scoring on the faces which you would expect from 250,000 km I guess.
Alternatively anyone know a place that can pressure test the pump output , I am based in Chester.

I used to have a volvo 250 and you could up the torque on the rack to compensate for loss of pump pressure in older vehicles which worked a treat. Can this be done on VW racks and if so how?
Kevin

[eltee]

what fluid are you using?

[Aidan]

Kevin
when I checked the vanes on another pump last week they were definately double ended , his were scored so I turned them through 180 degrees to give fresh faces, awaiting news as he had a lot of other work to do before being able to test the pump
new racks available from classic
I know where there's a complete used 2wd lhd diesel system too, and my other customer may need the pump off that.
I have a refurbished petrol pump on the shelf