525 TDS - hesitation on acceleration - possible causes ?

I have a 525TDS SE Auto 1995 which is now in generally good health, but I get an annoying hesitation when accelerating from about 2000rpm. It has been suggested that the fuel regulator/pressure
should be checked, but I don't know what pressure I should be seeing, whether it is possible to do myself without special kit, or where to test / what to look for etc.
It has just had a new fuel lift pump, glow plugs, fuel filter and new/reconditioned injectors but the problem has not improved since before any of these changes.
Can anyone comment on possible causes for the hesitation and way to test ?
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