His poops are becoming soft again and he has started using the floor again. The poops are not liquid as before, but I KNOW this cat. If he is pooping on the floor, he does NOT feel well. Call me crazy, but I simply feel this is NOT behavioral.
I have a call in to the vet about what we try next.
At least he seems to feel OK. It's just his tummy is upset about something.
DRAT! I thought we had found our answer.