i have been using z7 car wash for quite some time and i really like it . before i only used it on zainoed cars but now that i use other products like megs nxt,#16,p21s etc, it seems to take some of it off. so is this z7 wash a harsher wash than some others? i will be using it on my new bmw that will have klasse twins and pinnace souveran on it and i want a mild car wash that cleans good and gives a good shine but doesnt take any of my wax off. any reccomendations? i heard nxt wash it pretty good.