If you drill holes in the stainless steel plates at the end of the Corsa stock mufflers for better flow and a richer sound is there a chance you could get water in the engine even with the rubber flapper.Would it be wiser to just change the tips? I have a small block 5.0 mpi with stock exhaust. Which would be the best tips to use for better sound and flow?

Remove the mufflers and replace with Corsa baffled angled tips

Reversion takes place when the engine is shut down caused mostly by too big a cam