What does the inside surface of the chute feel like. If it is rough/rusty, that is the first factor as far as icing/blockage. Get the rust off and paint it with high gloss or graphite paint. The QL exhaust is the second factor to icing. It looks like you have an elbow on your exhaust pipe? If so, that should be all you need. I have a 45 degree elbow that I put on my exhaust when I hook up the snow thrower on my 1450. Since installing the elbow and painting the chute, my icing problems went away. You can ditch the heat shield.
Bill