In addition the the above great results with just a tune....check this out.
LG Motorsports put a C7 on the dyno with headers and no cats. I know the SS can make some nice gains with headers and no cats, but I didn't think they were quite this much!
Their testing with NO TUNE shows a nearly 30HP and 47TQ gain at the wheels!
http://www.camaro5.com/forums/showthread.php?t=322450