A turbocharged engine would benefit or if you had a ECU to program the tube for better air flow. Just changing the filter alone won't do anything.
Well once again I am glad I came on here before I wasted my money. Plus my Prius sure runs too good to screw up now! Never had a problem with this car! Got it with 11 miles on it now @ 105k still runs just as good! I was just thinking I could push it for a few more mpg, but I just learned that ain't so, so thanks to you guys!