Second Skycourier prototype, freighter version, takes to the sky.

Different stacks are probably to get the heat and soot trail up over the wing on the side of the engine with upward swinging propeller. Some Kingair stacks are slightly different angles too.

Check out the soot or bug patterns on the wing of a twin. You will see bugs under the wing on the side with upward swinging blade and less on the other. If a PT-6 the soot patterns will show a difference too.

I suspect without the stacks angled on the Skycourier heat against the leading edge might be a problem on the upward moving blade side of the nacelle