Does it actually affect the amount of fuel sprayed in? Seems odd, as the diesel doesn't care about A/F ratio.

I would say yes, thats exactly the function of the MAF. Got this from another webside (..loss of diesel power..)
......the condition of the MAF is crucial because this device helps the PCM determine the amount of fuel that is required to burn at the correct fuel/air ratio and thus the amount of fuel that has to be injected.....

It reminds you, that you have bypassed the EGRhttp://www.dieselplace.com/forum/smileys/Evil Smile.gifhttp://www.dieselplace.com/forum/smileys/Angry.gif