I'd stick with the tried and true Water Wetter. I've never heard of VR-12, but water wetter actually does work. It works by lowering the surface tension of the water in the cooling system. It effectively increases the surface area of the water contacting the metal parts, giving you better heat transfer. It's most effective on cars that are on the verge of boiling, the benefits won't be as noticeable on a system working within "normal" conditions. Since Vipers typically run so hot anyway, it wouldn't hurt to add some.