Will this bolt directly to my factory cat without any cutting or welding?

Yes — this catback design mounts at the factory connection point behind the catalytic converter. You'll connect it to the existing rear hangers and exhaust mounting points with no modifications needed.

Do I need to replace the O2 sensor or reprogram the ECU?

This is a catback system only, so it doesn't touch the O2 sensor or engine management. Install it and drive — no tuning required.

What fasteners and clamps come with this?

The assembly ships as a complete system. Verify all clamps and hangers are present before installation, and use OEM or equivalent hardware to secure connections during fitment.