Just in case you might be thinking of one, here are some comments from various Frontier & Xterra forums:
"honestly..just give me the money and ill punch you in the nuts."
"you'll get more hp with a nismo sticker."
"they do not work what so ever!!! they just make your intake whissle!!!" -has one installed, according to his sig.
"save your money and buy something else!!"
"they are good for 2 things, a great paper weight on your desk, 2 a place to drill and tap in a nitrous or CO2 nozzle."
"Yeah pretty useless, but it's a cool looking shiny thing to put under your hood . But seriously, save your money and get something else. I still have one on, but it didn't give me power, mpg, or better throttle response."
"The Titan guys swear by them, so who knows. I had one and couldn't tell the difference either way. Sold it on eBay for $50."
"The whistle is cool for the first 5 minutes, then you realize the you spent 15 minutes installing it, for what, a whistle? Then you think...how much did this cost? What was the gain? How did it sound? Wow, I just bought a whistle for a lot more than a buck!!!"
"it doesn't do anything but make your wallet lighter. lighter weight = faster."
"lol this thread is amazing..... Im going out to weld a folgers can to my exhaust for more power right now.... will post up later..... Might add some tuna cans to the intake for a similar effect"
"Look at all the suckers who BUY these things.
There's a TON of people who WANT them to work, just like they want the other magic mods to work.
People tend to believe what they WANT to believe, and to discount contradictory info.
Its EASY to prove to them that what they WANT TO BELIEVE is true, its almost IMPOSSIBLE to prove to them that what they WANT TO BELIEVE is false.
Its human nature."