2000 2.7 engine clicking, video included

I have a 2000 PreRunner 2.7L auto. No major modifications that I'm aware of. For the past two days I've heard a new noise. It's a fairly faint clicking noise that's in tune with how much throttle I'm giving it. I've included a video link that may help (you'll need to crank the volume).

I have a sneaking suspicion that I got some bad/watered down gasoline. Ever since I filled up (at a station I've never used before) the truck has been making this new clicking noise. Almost like the sound of a baseball card flapping against bicycle spokes, but not as loud. It happens whenever I give it gas, but not during idle.

Since it started, I topped off the oil and added a bottle of Gumout fuel system cleaner but nothing has changed. Any ideas?

VIDEO LINK

 

I couldn't hear it on the video. Have you popped the hood, and tried to locate exactly where the noise is coming from ?