Engine noise- revised

MY 2003 Altima with 2.5L is making an engine noise that sounds like a bad exhaust manifold gasket. Changed the gasket, but the noise is still there. Can hear inner engine noise.

Could the noise come from a gutted pre-cat? I see that it has a cat from a junkyard with crayon writing. Or possibly a cracked manifold???

Any answers, or guesses??