My V10 had it.
When my hood flipped back the wind kinda tore the fabric and it progressivly got worse.
I tried the duct tape as well, with no success.
I removed it for fear that the Fan or serpintine belt would grab it and remove it for me.
I havn't noticed a sound difference.

 

my hood alway shad one on until about 6 months ago when i started doing my paint project, i took it off since it was ripped, stripped the hood down and primed it and now about 6 months later you can see the primer starting to fade...so im going to wetsand it and reprimer it and when i spray the truck im putting a new one back on

 

oh and before i did my paint project, my hood looked perfect with the liner in and the stock paint...fyi lol

 

i dont have it either

 

I don't believe mine ever came with one.