Drum Temp and Cook time varies. You can not compare tests to each other.
Test #2, ECB Water Pan
I filled the water pan with hot tap water and let it simmer in the drum for 30 minutes. The drum wanted to run about 300* on the side with all vents open, so that's how we rolled.
Start 12:30 pm
Side Temp = 300*
Middle Temp - 258* after 5 mins.
Cook Time = 25 mins
Outside edge obviously a little hotter, but a more uniform cook than no diffuser.