Does a bad muffler really effect my engine performance that much?

[dagod16]

My muffler is at the end of it's life. I am positive it needs to be replaced. It has rusted through and the heat shield above it is hanging down on the muffler.
It sounds worse and worse.

Does is effect the engine idle or performance at all that I have a bad muffler?

How do I know if the exhaust manifold needs to be replaced? I don't want to replace it, looks fine, in fact I just want to replace from the left of the convertor back, so I will keep the convertor.

[bigjim350]

A worn out muffler will only affect performance if something inside it blocks the exhaust flow, which can happen. As for the ehaust manifold, the only reason it would need to be replaced is if its cracked and has a bad exhuast leak, however it still isnt a "must" that it be replaced.

[Joliet Johnny]

With a muffler like that you may also missing the much needed back pressure. Its an either/ or situation.

[dagod16]

Well the cat seems fine but my muffler is shot for sure. It's on the shopping list, probably next month till I do it. I need to feed my children first hahahah