300tdi misfire

hi have a 94 disco with 300tdi in
i have given it a full engine service inc tappet clearances
sedimator is bypassed
refurbished injectors by good local specialist
checked boost 15psi@3500 rpm
new delphi lift pump
new leak off pipes
changed cambelt
fitted an egr blanking kit
cleaned inlet plenum
washed out intercooler
still got a misfire starting around 1800 rpm and continues throughout range its an auto so not expecting a rocket ship but its more like a snail than brian
only other thing i was thinking was to do a compression test but i dont have a tester
am left thinking that its the fuel pump but wondered if i was missing something
hope someone can help
cheers kev