I am another who has not benefited from Heather's Diet...giving up is giving in and you both have too much going for you to quit now.
I kept trying (I have had IBS for 22 years) and modifying my diet until I found what worked for me. Keeping yeast and refined sugar to a minimum and paying attention to my own triggers and really not worrying about what did or did not work for others is what has brought me to a stable point.
These boards though wonderful can also be a detriment in a way. I think if we were all honest with each other it is somewhat addictive and you can obsess over stuff which is unhealthy.
Focus on yourself and listen carefully to your bodies...consider other peoples "fixes" but try not to get frustrated if they don't work for you. IBS is an inexact science.