i run rainx' 2 n 1 which is -25 no problems so far. I dont think it will leave deposits unless you leave it on and it just runs down into your intake while the engines not running
I was tol to run the -20 Peak. That is what Snow Performance reccomended. Unless I mixed my own or bought their boost juice. I don't see how it would leave anything behind unless you shut the engine off directly after using it.