Hm. I guess I should try checking that. I realized later on that the sound I'm talking about could also be described as somewhat of a very low hiss, so I don't know if it could be a vacuum leak somewhere. It does sound like it comes from the driver side of the engine bay too. I did look up videos of people showing that knock/pinging sounds like and from what I could make out it doesn't really sound like what I'm hearing either.
I am thinking though when it's time to refuel (I usually do when I have 1/4 tank left) I'll try higher octane fuel to see if there is any improvement..
