Is there a nusach hat'fila in which the 16th b'racha of the amida begins with "אב הרחמן" at shacharis only and skips those words at other t'filos?
I heard recently that this is in fact printed in some version of the Artscroll Siddur but I have not seen it inside.
Why would this be so? Isn't one consistent with nusach S'farad and the other with nusach Ashkenaz?