ok I had to try an experiment! seeing home is old and easy access to attic snagged a nice fresh piece of fiberglass insulation to use in all 3 smoke units on this BB.
I also learned how to remove the blowdown tube from the BB frame as the side blow down outlets are a friction fit.
after I removed them and the 2 screws holding the blowdown tube to frame and the red firebox feature pcb out it comes.
there is a raised area dead center of main tube so smoke will get diverted to both left and right side exit holes.
I am including a video and mind you the cab-2 is set to low smoke setting and what you see is what I now get.
I see others have videos but thought this one should be posted seeing that I'm using something other than what it came built with.
as a side note the heat sensor for smoke stacks if the optional cover is put in place has a small screw that holds the pcb in place mine decided to pop off and have no idea where it went so found a replacement in my spare parts bin.