I LOVE LOVE LOVE (aka am addicted to) Guthrie's. However, I have (sinfully) become a Zaxby's convert since I now live next door to one. I haave noticed that their sauces taste VERY similar and I know that the "secret" ingredient in Zax sauce is anchovy oil (mixed with mayo and ketchup, I believe. If you asked at Guthrie's, they might just tell you; you never know. Happy dipping!