I wonder if any of you can help identify the pipe/ exhaust/ vent? present on the T-64 photo below

I've added it to my Skif T-64A build, but wonder if it should be open (as it seems to be in the various walk arounds on the web)
or capped (as I've seen a number of walk around vehicals with missing fuel caps etc, especially when they are stored outside in reach of the general public