no revs

hello there,new to forum so excuse me if i sound daft. av got a p38 diesal that i've spent a fortune on, was running spot on on but now hav lost all revs,had it plugged in and came up throttle pot fault, changed that still same, i've had a donor r r at the side of mine and used there fuel system so it rules mine out and still no revs, i fitted a recon injection pump 2 months ago am wondering if its down to that. has anyone got any ideas before i go and shoot the the guy that refurbed my pump ??