That is weird... I'm lost...

I may be going out on a limb, but I say clear the code as you pull up to the place and then let it pass emissions and be in the clear for 2 more years. Milly is acting up, Shame on her for throwin the P0400 code! I'm sure you took care of the EGR valve, soooo I REALLY don't know why you've had this code for SOOOO long. I say clear it before emissions are due.