long time no see.
i added a toyota cai to my sequoia 5.7l v8 4wd a while back.
1. mileage. local: 18mpg, hwy: 22-23 under speed limit, and down to 19-20 if over 65-75mph. better than EPA 13/18. it definitely save gas. i have a calibrated trip computer to confirm this. this is better than my wife's v6 suv.
2. cost. no need to replace, just to clean every 20-30k miles.
3. power output. about 9hp increase conservatively, this is confirmed by dynograph (pls check my spelling) from manufacturer.
i always think people should run faster when they are not having an asthma attack.