your pump is a good pump, it's an interpump w965, does 250 bar (3600psi) at 15 litres, make sure your nozzles are size 04, (2 x 02 on a whirlaway) with the correct nozzle on (04) run it and it should be producing 3600psi, look on you gauge to check, if it's doing less then 1st check if your unloader is not unloading, if it is then tighten it up untill it's not, if it wasn't unloading in the first place but your still under pressure then adjust the throttle governer screw so you produce more revs (it may have been turned down at some point) still not getting the right pressure? get a new set of seals, also pressure feed it to see if it leaks any water, if it does you may need new pistons aswell as seals, check them
The good thing about your machine is that you can't break it, ie you can always get spare parts, hence, no nedd to buy a new one... unless your engine seizes or something major
Keep it and tidy it up as matt says, just look after it and it will last you for years