Dippydog could be right...Try read the MAF temp without starting the engine and see what you get...the MAF it's also "inside" ...
I am keeping mine into garage and we have above 0 celcius temps for the moment outside ,but if you are not in a hurry ,I would check it on mine too(same car/engine but 2004 made)...
Though I would rather blame the injectors...Welcome to the OLD DIESEL ENGINES REALM
