discovery 300tdi lacks power + intermitant ticking HELP!!!

hi i have a 1995 discovery 300tdi and am currently having some real head scratching issues! basically i bought the vehicle with a blown headgasket and repaired this thinkin it would all be plain sailing once done oh how wrong i was. the head gasket has been a complete sucess but now its running and can be driven readily i've noticed a severe lack in power and a ticking which believe to be diesel knock, i draained the sedimenter and changed the filter then bleed the system and it fired up quiet but still seemed down on power when driven as if there was no boost and after several miles the ticking came back quietly at first then gradually got worse! we decided to have a quick look at the diagphram and notice it was stuck in 1 position and couldn't be removed then after some wd40 and working it a bit we managed to remove it and there was a clear dot on the cone where the fuel pin has obviously been sat in 1 place then we noticed the fuel pin appears to be jammed and isn't following the cone but there is boost pressure through the feed pipe to the diagphram god knows what to do can anyone help please???

Tappets ? Timing ? I'm just guessing randomly though


You'll be wanting a forum member who knows more to come along

tappets down at same time as head was reconditioned so only few weeks ago and i don't know about timing as it intermittently runs ok