Actually, peanut butter is fine - it's fairly safe protein so long as you don't have loads of it. It's definitely one of my staples!
Oh, and garlic and onions are just fine with me (particularly when they're cooked well). I'm ok with spicy food, so long as it's only once or twice a week. I'm not a real heatseeker (outside of the great hummus with hot sauce I got the other day - yum!), though, so that may not really be an IBS limitation.