I vote for off. Mine came with those same louvers. I thought they'd grow on me, but as soon as I went to get my windows tinted they were removed.
There are some styles of quarter window covers that look good. The louvers the factory puts on as part of some of it's packages just look cheap and tacky.
I vote for off. Like someone else already said, I like some of the quarter covers but those are not one of them. I'm not a big fan of the side scoops either. And on that note, the GT/CS package as a whole looks okay but I absolutely DESPISE the stick-on hood scoop. It just doesn't work with the car at all. That said, I'm glad you don't have one. :beer:
Off. Hate them(personal opinion). The flush mount ones look a little better but I still am not fond of them.
And another vote for side scoops off as well.
leave them on. Not everyone should have the same looking 5.0. Make yours different and leave them on. Nothing wrong with the side scoops either again be different.
I don't know what the big deal is with the louvers and side scoops.