Important Background Info: The air cleaner is equipped with two inlets, one of which is opened or closed by the Intake Air Control (IAC) valve #3. This system reduces intake noise. When the engine is operating at low to mid speeds, this system operates the IAC valve to close one of the two air inlets. When the engine speed is more than 3,200 rpm and the opening angle of the throttle valve is more than 30 degrees, the ECM activates the Vacuum Switch Valve (VSV) and opens the IAC valve #3.
We will re-route the vacuum hoses so that you bypass the VSV and connect IAC valve #3 (a.k.a., the "flapper valve") to a constant vacuum source. This will keep IAC valve #3 always fully open at all engine speeds resulting in less air flow restriction, decreased throttle lag and some improved low-end performance.
This photo of the inside of the air (filter) box illustrates my point (photo credit: SWIFTOY) ...
The small opening (labeled "1") is the only air intake source for the engine when IAC valve #3 is closed. On the stock set-up the only time IAC valve #3 opens and allows air through the large air intake opening (labeled "2") is when the when the engine speed is more than 3,200 rpm and the opening angle of the throttle valve is more than 30 degrees.
With this mod, the large air intake ("2") is open at all times allowing about 4 times more air flow AND without any delays from the ECU to sense engine speed and throttle position, then trigger VSV #3 to FINALLY open IAC valve #3.
This is a photo to orient you as to where you'll be working (the parts in question are in the yellow circle).
Here's a close-up view. Disconnect the two vacuum hoses at the points as indicated in the yellow circles.
Now reconnect the vacuum hose going to IAC valve #3 to the open port on the "T" connector. That's it, you're done!
If you want to "do it up right", you can buy about a 6" long piece of 5/32" (I.D.) vacuum hose and two 5/32" vacuum plugs (caps). Connect one end to IAC valve #3 and the other to the "T" connector, then plug the 2 open ports on the VSV to keep any dust or dirt out. Keep the two pieces of stock vacuum hose in your car in case you want to reverse this mod before you bring your car back to the dealer for service, etc.