I see a few guys building engines with them, but haven't heard any real numbers, or opinions. I'm assuming they're giving up some mid range torque, and come on up top (5000+ rpm), but you know how that goes. I picked up a nnbs intake, and plan to run that unless these are better for a 6500 rpm build.

 

keep your nnbs. 6k-6500 is right when the sheet metal starts to pull away. Until then its a boot stomping. I've done a fair amount of dyno work with them and they really kinda suck until you get up in the revs. 30 foot pounds down at 3500 on a 6.0 NA swap is pretty normal from what I've seen.
Problem with any stock options is they are all ugly as a mud fence. If you can stomach looking at them, and they clear the hood, they are really hard to beat on a street car.

 

Thanks, that's kinda what I assumed. I don't mind the looks, and have room.