Ian i,m having similar problems to you ( I have a 2001 Disco TD5 Es Auto), have blanked off the egr, new air filter in, and then problem started RobCSH said take off the boost sensor and clean it but I have know idea where or what the boost sensor is ( would like to locate and clean as a precaution). So in he meantime i've taken the plug out of the maf sensor now seems ok. I take it that this is the problem, so a new one will be on its way, how long can you leave the maf unplugged for. Is yours still disconnected or have you put a new one in.
Steve
Steve