Has anyone installed a cold air intake with good results on improved fuel efficiency?

The cold air intake is to help increase HP, when you increase HP, you lose MPG in most cases. Normally I have found that when you put a cold air in a car you get a increase hp and most of the time you lose MPG. The 4Runner isnt known for fuel mileage as almost all the ones I have seen get about 15-18MPG. If you keep it tuned, and do he oil changes (5w30, helps a little). Also all those "fuel wonder mileage increase" add ons dont work, as all have been disproved through the EPA or independent testing (Mythbusters even did a few shows on this subject). But if you go to http://www.fueleconomy.gov/ you can read up on it. Just keep it tuned and stay on top of the service. I have seen my brothers 4Runner get just over 20MPG on the highway. Best of luck.

I have found a K&N air filter will give a slightly better MPG and different intake note, as it allows more air through to the engine.

Cold air intakes increase overall engine efficiency, so it will increase horsepower, torque, and MPG's. However, the MPG most likely won't be significant enough for you to notice it right off the bat (maybe about 0.5 MPG better)

CIA is a waste of time and money. With a dremel tool and a little know how, you can do this modification for increased efficiency, power, and a nice tone. http://www.yotatech.com/~corey/tech/dr_z_intake/dr_z.htm

More air into the engine, more fuel to keep it at stochiometric. It will take you a long time to make up the money for any (if at all) fuel mileage gains you will see. Some vehicles benefit, some do not, yet the parts get marketed as they do the same thing for every vehicle. Every vehicle has a different design for their intake, not all are restrictive.

I own a 2003 4Runner V6 LTD and managed to improve my MPG considerably by doing some surprisingly simple things. Firstly I had the engine flushed at CAA with a non chemical pressurised charged particle fuel flush, then I replaced all of the spark plugs with E3 high efficiency plugs, vaccumed the air filter and lastly pumped up the tire pressure (during the summer months only!) to max which on my tires was 46PSI. These changes which in total cost me about $200, increased efficiency from 400km per tank to 600km per tank, a 50% increase! And they remained in effect afterwards, they weren't temporary. I also noticed that I retained pretty much the same level of fuel economy after these changes independent of how I drove, all in all well worth the money spent :)

Oh, I checked out the pros and cons of air intakes too, but soon came to realise that it really isn't a good idea as the only way to increase air is to decrease protection and allow more damaging particles into your engine. Not really a good idea if you want your 4Runner to last.

Oh and the last thing I did was change the oil filter to a 'tough guard' and the oil (which I bought at a US Walmart sale for cheap) to Mobil1 0W-30 Fully Synthetic.

I put a Stainless Steel racing intake w/ an open air K&N element, and let me just say for less than $100 K&N dynoed the set up at 9.4 hp for the 4.0L......should be close to the same for the 4.7L. Oh and have you figured out at which speed the best mpg is achieved? My sweet spot seems to be 85mph, consistantly 24mpg+