The car has minor issues that I will address in the future, but this is annoying as I hear a rattle from under the car when I accelerate.

What could it be?

 

really hard to tell, but could be a heatshield or cat material disintegrating. You would likely want to put the car in the air and tap various parts of the exhaust.

Alternatively, it could be tensioner related, but you'd need to put the camera by the engine bay to get a better idea.

 

I'll have to take it to a mechanic to use their ramp.

Tensioner, hopefully not. I do need to check if it has the metal tensioners.

When popping the bonnet open, I hear a tick every few seconds. Hopefully, that is not the tensioners.

 

The tick under the hood might be normal.

I had a weird rattle under my car under acceleration, only happened at a certain rpm/load combo. Didn't sound too loud until I drove with the windows down and realized how loud it was, sounded like the engine would come apart.

Turned out to be the center shared muffler, something failed internally and would rattle at that certain rpm. Replaced it and noise went away. Still have the broken part to perform an autopsy on one day if I get the urge to.