I live on pretty flat ground at almost sea level and I've install more cold air kit's and cat back exhaust than I can keep count on. In most cases those people that buy them actually change their driving habits after this stuff is installed and get less MPG than before. Simply becuase they feel the need to feel the "Newfound" power. Any time you can cause an engine to breath more freely it will make it more efficiant but don't expect what the manafactuer claims in MPG or horsepower. People who look for more power find some because they drive the wee out of their car after the install and in their mind justify the money they spent on the mod by holding it a little tighter a little longer. Those looking for more MPG tend to drive just a little more on the egg shells. Nobody wants to think they wasted their money. In most cases it will give you good results either way you go. It makes the engine more efficant and thats what it's all about. Is it worth it? In the cool factor, mpg and power I say yes. If you are looking for a drastic change in fuel economy it isn't going to be there. Your driving habits make the most differance and it's free. Just being realistic, JWConsidering getting the magnaflow and intake simply for MPG purposes (I usually drive like an old woman unless I'm merging) so extra HP really won't benefit me.
I whipped up a spreadsheet that lets you play with your own MPG range, a projected increase in MPG and cost of gas to allow you to figure out how much you're going to pay for gas over the next 30k miles with and without mods.
I'm looking for specific input from owners of these mods. How much MPG increase did you see from each? For the owners of both, how about you? What is your driving style? I'd like to save money on gas if I can, so presuming I'm going to be driving this for a while, it would be nice to know if the long-term savings are worth it.
Also, as always, run a virus scan on any downloads if you're unsure of what may be in them. If you don't want to download it, DON'T! It's as simple as that. You don't need to play with the spreadsheet to benefit from this thread.