I guess to simplify my question a little more.

Would a muffler with the same outlet size in sq mm the same size as the inlet cause a engine to over heat and damage the engine. ????

I think I know the answer but would like to get some input from others about it.

I understand how a tunes pipe or canister work’s, could never actually make one, but do understand how the right amount and at the right time back pressure can hold more fuel in the cylinder for better performance.

Milton