www.google.com

Needs a resonator.

Put a glasspack in, they're $30~. Bigger the better.

This topic has been covered a million times, just look around.

Use whatever mufflers you want, the factory "Y" will be reuseable most of the time; for a downpipe, get a stainless 3" one from ZZP. Catted or catless is up to you.