Difficult to say whether I gained or lost any hp.
I bought it for the optics and sound, imo the perfect cai. I prefer the looks over a pop charger, although the Typhoon is more expensive.
I got mine from eBay as it worked out the cheapest. Also I got the 'new' polished version. The old polished version had a blue rubber piece connecting the throttle body and the airpipe. The new one has a black one, which imo looks better. I think that's the only difference though.
Model # for 'new' polished one: 69-7070TP
I bought it from this guy, shipping was 75$ for me (to Belgium)
http://cgi.ebay.com/ebaymotors/K-N-Typh ... QQtcZphoto