I don't recall ever having had a problem with the WOW potato chips, although I didn't like the greasy film they left in my mouth and so have avoided them for that reason. I seem to recall I tried them again a few years back and didn't get that same greasy aftertaste, but for whatever reason, I just kept using the regular chips all the same.
There's a new prescription diet drug out right now that's supposed to be really horrible about causing you to mess yourself. Someone jokingly pointed out that it only caused you to lose weight because you got too scared to eat. I don't know if that's 100% of its ability to work, but there are certainly a lot of people on here, me included, who can attest to the fear of eating being a source of weight loss.
The other things to be on the lookout for are sugar alcohols. They give everyone gas and D if you eat more than a few pieces of sugar-free candy; I could certainly see how they could cause D bad enough that it caused leakage.
GCutter, you mention itching. That sounds a lot like a hemmroid. I wonder if you have an inflammed hemmie that might be keeping your anus from closing up all the way properly? I don't know enough about hemmroids to know if that's possible, but I know when I get itching down there, that's the cause of it. You should probably have a GI check out out down there and see if that's the case. If you can't get in or can't afford to see one, you might try some hemmroid suppositories and see if that helps the itching and/or the leakage. If the itching goes away, then that was probably the cause.