Any seals that fold downward or backward will allow air to bypass the cylinders. Black rubber baffle seal material is trash. It typically loses its sealing ability in just a few hundred hours. It will last to TBO or beyond. Fix exhaust leaks immediately.
Exhaust gas is incredibly corrosive.
Small exhaust leaks turn into big ones amazingly fast. Exhaust leaks often occur at the cylinder exhaust ports where the exhaust riser flanges attach. Leaking exhaust quickly erodes the soft aluminum at the exhaust port, necessitating costly cylinder removal and reconditioning. Exhaust leaks are easy to spot. They leave telltale red, orange, or yellow stains.