Re: Why is this happening?

[Mumbles]

I think it restricts the amount of exhaust going out the idle relief passage so it doesn’t become the main exhaust outlet. Not really necessary for the motor to run but it is there for a reason. The 50’s classics had tubes on the plate and yes, they would occasionally come loose to. If you clean the threads and use a bit of Loc Tite, it won’t go anywhere.