I don't have IBS, just gallbladder-less but I know what you are talking about. Mine isn't as sudden in onset but it can be painful and an urgency a few hours later. I really try to balance in meats, cheeses, and some carbs when I eat salads and things like that. It has improved over time and my digestive system has seem to adjust so it's not as bad as it was at first. I remember having to baby my digestive system for a good while. I also remember the first time I'd eaten fruit salad all by itself and discovered the new issue...

That was when a good gallbladder-less friend suggested I eat proteins and carbs with my fruits and veggies b/c it helped her.
I haven't head of the Phillips colon health but it's worth a shot. I might give it a try myself.