Hot engine + solvent seems to help. Nothing will do as good as a manual cleaning.
In my case I used Seafoam aerosol, CRC came out with a specific product for DI buildup.
E-Mail seafoam sales to get an exotic application straw (Melted end shut and 4 holes poked into the side, makes a nice mist cloud) and pick up a rubber stopper from a hardware store. Drill hole in stopper, push straw through stopper and insert the contraption through the IAT sensor hole on the manifold.
Took off a lot of the darker buildup but left the light grey baked on deposits.