I will say that for us anyway I have to feed less than what is on the bag for TOTW otherwise mine get the runs. Overfeeding is the #1 cause for diarrhea. So you might want to substract 1/4 cup of food a day (not per feeding but per day) and see if that helps at all.
I wouldn't go back to Iams regardless of if he gets solid stools or not.
Tyson, white, 4 years, Boxer & Thor, 2 year old GSD
Tiger and Raven, kitties, 10 and 11 years
Erin flashy fawn, Lucas, Flashy Fawn, Boxer angels, RIP 11-29-10 and 8-22-07