When we lived in South Bend there was a tiny, delightful, store front Thai restaurant downtown that had the most amazing tofu stir fry (for lack of a better title or term), Thai spring rolls, and a sweet and sour sauce for the spring rolls that was simply amazing. It was a perfect blend of sweet and savory/sour with a hint of heat. I have drooled for that sauce time and time again. Tonight, I think I found it!