I too had been diagnosed with IBS and went through the high fiber supplements; and like you - I found that the high fiber increased my symptoms instead of helping them. In simple IBS - not associated with adhesions - it is true that high fiber will help control symptoms.
I saw Dr. Willam Richards at Vanderbilt in Nashville, TN. He taught me some very interesting things about the bowel and adhesions. First thing he said was that the bowel does not interpret pain signals the way the rest of the body does. When he enters the abdominal cavity during a surgical procedure, he can manipulate the bowel, cut it, etc.; and the body does not intrepret that as pain.
What triggers pain in the bowel is distention. Adhesions - that attach the bowel to itself and to other organs - can interfere with the passage of gastric contents and cause distention - and therefore the perception of pain.
When the bowel is "full" with fiber - and the fiber reaches a place in the bowel that is attached or affected by adhesions - this prevents the "normal" bowel contractions as the peristalsis of the bowel tries to move the fiber through. Things get backed up and not only cause distention but also causes pain.
The complicating factor is the IBS. A person with IBS has a much lower tolerance to bowel distention. Research - done on patients with IBS and patients without IBS - showed that when a balloon was placed in the person's rectum and inflated, the patients without IBS tolerated bowel distention levels at nearly 10 times greater than those with IBS. So those with IBS experienced high levels of pain with the same level of balloon distention that caused no pain in those without IBS.
The least bit of distention can trigger major pain levels in those of us, who have both IBS and adhesions. This also explains why our symptoms of a partial bowel obstruction (elevated white count, vomiting, diarrhea, and a high level of pain) won't necessarily be picked up with x-ray.
Dr. Richards told me that I was more than likely nearly obstructing during these episodes - and he could go in and take out the part of the bowel that's causing the problem; but until it actually shows up on x-ray, there isn't much he can do.
He also told me that there has not been any research done to try and establish what is a "normal" level of bowel contractility and what is abnormal. He is actually in the process of trying to develop an instrument that can measure bowel contractility so that some range of normal can be established. He told me to stay in touch with him - as he hopes in about 1 year's time the instrument will have been developed.
Back to your origional question about diet - a low residue diet does not usually cause the bowel to be distended like a high fiber diet/supplements can. For a person, who is dealing with IBS and adhesions, - preventing even the least amounts of bowel distention will help to prevent major pain levels.
I hope this has answered your question and I haven't confused you.