What Can Cause Bloating, Pain, Gas And Diarrhea (sp) After

what can cause bloating, pain, gas and diarrhea (sp) after meals or even a taste test. also different colored bowel movements? orange, yellow (watery) pale, gray once, and normal at times. sometimes foamy or mucus.
there is also a smell like car oil at times. been diagnosed with IBS but I wonder if it's more. I had my gall bladder removed in 1992. I have an autoimmune disorder (IC) just curious because it rules my life.