Sorry tuner, I didn't realize you had an '03.
To address your question: On the 08's, a tune shouldn't be required. However, I had a custom tune, which I reflashed back to stock after installing the intake to avoid any issues. I'm not sure about the Typhoon requiring a tune on the '03s. I'm sure it doesn't, but it would be better to have one.
With that said, I'm going to have to echo 04wrxharts advice for the most part. Your intake system is more efficiently designed than mine. All I would do is remove the silencer from the passenger side fender well and replace the filter with something higher flowing. Also, I would highly recommend a GP Moto intake elbow, they run around $40-50 and are designed to replace your silencer with an elbow directly re-connecting the air box to the rest of the intake system. That helps maintain the Ram Air effect of your stock inlet scoop.
I am bolting on a Turbo that's capable of over 300 whp, and I didn't want my factory intake system to pose as a restriction. That's why I got the K&N Typhoon. If your goals are more modest, then I don't recommend it. And with an aftermarket intake, expect a loss of power in the lower third of the rpm band. It's only when the engine is consuming lots of air that it could potentially make a bigger difference. And of course, I recommend a tune.
In short, an intake would be one of the last power modifications I would do. Hope that helps your decision.