Good link to the Autospeed article...
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So GENERALLY SPEAKING the most effective mod would be to leave the OEM paper filter alone...remove the snorkel and open up the intake on the bottom of the filter box...reducing pressure drop by maybe 9" water and providing minimal warm air in the process.
"in the summer warm air will provide a slight gain over cold air , heated air in winter will provide a larger gain over ambient temperature air"
....have seen no proof of this...but it is what I suspect is the case.
If you look at this graph...I drive at around 2K rpm for mpg gains...so ANY MODS will probably be
almost ineffective...but might show some gain on the rare occasion when caution is thrown to the wind....
I like to do mods...but don't like wasting $ on them...good to know which direction to go in....