injection pump timing

hay guys.

my disco just failed mot on emissions due to smoke.its had new filters new lift pump,new oil,my next stab to stop it is either the injectors or the injection pump.theres also a problem with it not revving passed 2000.i had welding done to the boot floor and they removed the tank,ever since then it ran like a bag of ****.so i took it back and they cleaned the fuel lines and the tank and its still no different.i did have a cam belt put on and have been told that you have to lock the pullys in place,ime not sure if that was done so ime thinking the injection pump might be out of time and with the fuel system being taken off and put back on with bad fuel timing thats why its not running properly,it smokes like you wouldnt belive and theres a bad smell of diesel when it runs,it starts and idles ok but when you drive it it wont go over 30-40 mph.so what ime asking is that technicly if the pullys dont line up with the pin holes then its out of time and needs adjusting?someone please help ime without a car with a family and its hard work.

if its 300 or 200 tdi you can check pump timing by fitting pin in flywheel housing and pin in injection pump through access plate on timing cover you may need to turn engine twice to get pump in line ,but to check cam timing is right too you would have to remove front cover to align marks