exhaust

Currently the joining of my inlet pipe and muffler is above the hood and it leaks, leaving exhaust residue on the hood. When I purchased the tractor, there was no clamp there. Thinking a clamp would stop the exhaust leak, I added one......to no avail. It still leaks. Having seen numerous make do...

:( I started driving tractors in the UK 60 years ago and I have never seen here a tractor exhaust with a flap on the top but in the US they're quite common, especially on older tractors. This is probably a rookie question but what is the purpose of the flap? Please be kind with your answers!