For the price I'd personally rather take the bumper off and find out why/what's making the sound . as far as putting the dampers inside your engine it's just not a great idea. I hope you meant engine cover instead of valve cover 
What that mean ?snake oil, just don't see them doing anything.
It means a fraudulent claim, something that can't be proven to work.What that mean ?
I already ordered so lets see, also its Hyundai oem part so my hopes are bigger ..It means a fraudulent claim, something that can't be proven to work.
I just took engine cover off .Interesting. Were they easy to install?