I have been seeing alot of these on eBay lately. I'm not so much interested in if they work or not, but how they say they work. They say that they fool the ECU into thinking that the air coming into the intake is colder than it actually is and will adjust the the air/fuel ratio accordingly. My question is, are you damaging your engine if you make it think the air is cold when it is hot?

They have been on Ebay before the RX-8 even was for sale, the seller just adds RX-8 to the listing for the other mazda "chip"

http://www.rx8club.com/showthread.php?t=47162 should answer your question.

Making a fuel system richer when its already rich results in a power loss.