Possible rod bearing failure? HELP - weird rattling sound from engine bay

[gor]

Hi all, so I'm having some weird ticking sound coming from the engine bay. Not an expert mechanic by any means so I'm not entirely sure what it is. Here's a sound clip:

https://www.youtube.com/watch?v=-1p6...ature=youtu.be

The rattle increases with RPM's and can be heard only when I'm on the throttle. The sound disappears once I let off.

Recent updates with the car:
- AC sometimes gets really hot while I'm idling. When I get moving, the air blows ice cold again. This only happens sometimes.
- I just changed the oil and filter on the car using 5W-30 fully synthetic oil and a K&N filter. When I drained the oil, only about 2 quarts came out... This really worries me. (I just bought the car - drove it about 1500 miles before the oil change. It's at 95k miles)

I really hope this is not a rod bearing failure or something similar, but I'm thinking it might be. I've also got suggestions this could be an exhaust heat shield, but I have no clue. Any suggestions would be appreciated!