This has been discussed and pretty much proven that the open grill has benefits. How could it not? Its common sense. There is a reason the boss has fog light deletes. At the same track within 30 minutes of passes, I picked up 1 full mph in my '13 boss with the fog light piece REMOVED. I removed the fogs in my current '14 gt and can feel a difference as well as 1 more full mpg with the same driving habits. There is also a video floating around of an open grill car pulling a non open grill car with approx the same mods. I believe they also did some factual testing that proved the open air had clear benefits for air flow/temps etc. All I know is it works.
Kevinp- funny you mentioned vararam! I ran one on my old C5 and there were obvious gains with that piece, even un-tuned. I picked up nearly 2 mph in the quarter with that piece alone. At 80mph, much better throttle response and definite seat of the pants difference.
See, told you on the vararam
If you can get some cooler air to the filter then fine, thats about it.
If you believe its helping you out I'm not going to pee in anyone's cheerios. But i have pickup tenths at the track and done nothing except eat a chili dog