An SRI for 2011 Elantra not avaliable yet (some people had to use an intake from a different car and mod make it fit). For .I couldn't find the specifications of an intake that will ,so I just played around and got SPECTRE intake parts from Pep Boys and a few hours later the job get done! Not as good as a "brand name" but good for me.

Parts used:

Intake tube 4" long $8.99
Intake tube coupler $7.99
Air duct filter adapter $5.99
Intake tube 60 degree $11.99
Cone air filter $19.99
Vacuum/sensor/adapter kit $7.99
Hose clamps 3.5" $2.99 total $71.27

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Take off OEM tube, filter box cover and filter

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I cut 1" out of intake (tube was a little too long)

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Put coupler on intake tube (in pic I don't use vacuum sensor... adapter is too long)
Connect duct filter adapter to 60 degree tube

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Drill a hole on 60 degree tube for sensor tube(vacuum/sensor adapter kit come with 2 bits lg & sm)

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Put air filter at the end with hose clamps.

The test drive sounded sweet. A little louder than normal and more power. Takes this Elantra to a new level!