I've seen a few threads about HOW to remove or gut the air pump (smog pump), but none of them really address the WHY. Has anyone done this and got better mpg, or a noticeable performance improvement?

 

If you have removed or gutted the cat, the air pump is pretty much jusr dead weight and a paracidic draw of power from the belt.

 

Agreed, once the old stock cats are removed or gutted out the air pump is useless and unless you live in an area where the smog ****'s won't let you remove it and pass the test I say delete it and call it done. All you need is a shorter belt.