I have those on my Harley. It's a venturi sleeve that creates a vacuum to suck out the exhaust gasses a little faster. I think they were called torque sleeves, but don't quote me as its been a long time since I got mine. they're not stock, but nice that you have some. If they're not damaged, clean them up and reuse them. Otherwise, leave them out.
Found them in my harley book
I'm not sure if the Harley ports are the same size as yours or not, but they may be.