I've got a mysterious rattle coming from under the hood that happens only when driving between 1200-2200 rpms. Its a little louder going up hills. Took it to a mechanic and got these codes: P0171, P0420, and the IMA code P0A7F.

Could be a broken cat? or a tensioner? Anyone had this sound before?
Mechanic looked at timing chain and its fine he also adjusted valve clearance. He didn't look at the cat converter because he claims the sound went away after he did the valve adjustment, but nope started making the sound driving away from the shop.

The sound is most heard at the end of this video:

Stats:
2006 HCH
174,000
Im the second owner