How To Remove The Stock Air Filter Box

Detail of the original air box.

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Using the large image as a reference you need to first remove all the clips from around the edge of the box, then use a Phillips or cross-head screwdriver to undo the pipe clamps on the large intake tube. The solenoid mounted on the side of the air filter box should be left connected to its wiring and larger two tubes, although it must be unclipped from the air filter housing. At this stage the MAF sensor should be left in its mounting position and the wiring connector unclipped.

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Air filter box cover removed.

Once you have removed the air-box lid this is what you should see.

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Remove the air filter.

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Undo and remove the two bolts holding the air-box in place. One is to the left the other is in the front slam panel.

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Turn the air filter box over and you will see another valve with three small bore pipes attached. One of them should go to the engine, the other two connect to the air filter box itself. Undo the blue cabling connector and also disconnect the pipe that goes to the engine. At this point you should use the short rubber bung supplied in the kit to cover the outlet on the engine. Leave the valve connected to the air filter box, you won't be needing it.

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You can now remove the old air filter box.

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And the old air intake pipe.

Source...
http://www.celica-club.co.uk/pages/modifications/performance/blitz_intake/remove_old_box.htm