I haven't always been on enough to remember if Diesel has any specific food issues... but it seems strange to me that he would need to poo every 2 hours. You said it's nasty? Like loosey-goosey? I wonder if he has a "bug" in his track, or a metabolism issue or something.
Bella goes two-three times a day, usually once in the morning, once in the evening and sometimes on our walk at the park. She gets fed similar to Koby; once about 7:00 am and then again at 7:00pm. I guess I don't know Diesel's whole story, but it seems like things are "moving" too fast in his system, ya know?