From what I've heard, due to the Mr. Freeze kit working off a vaccum line, it simply draws the water/meth from the reservoir and "sprays" it into the intake piping before the blower - people are concerned because how well can it spray if it's working off a vaccum line - the water/meth won't atomize as well as opposed to being sprayed after the blower, such as that on a Snow Performance kit. The Snow kit has a pump that goes with it, making it a bit more expensive but offering better atomization.