Loud rattle from engine, 1500-2000 rpm - SOLVED!

'01 Forester with about 213k

Engine makes a rattle like noise when revving between 1500 - 2000 rpm or on cold start. Sound appears to be come from around the A/C compress or behind. My brother loosen the belt attached to the compressor and thought it was unlikely coming from it. Here is a video that demonstrates the sound: https://photos.google.com/share/AF1...?key=b1hCU1hUQUFaZXcxTjRmRVhEYUpEcmNNRndQallR

Watch with sound on. No check engine light

Head gaskets were done a little over a year ago. Recently had an o2 sensor replaced (check engine light went on when I had this issue).

Thanks for the help.

Chris