I recently changed my engine air filter and spark plugs, and while doing so you must necessarily remove the air intake box to access the Coil-On-Plugs and the plugs themselves. This is all incredibly straight-forward stuff, and so I'm not here to give a write-up on doing that unless people are really keen on getting one. What I am here to talk about is the Mirage air intake assembly. I want to confirm what some other users have said regarding removal of the intake resonator/snorkel tube, and also to suggest some alternative ideas about what is going on with these removed.
The main airbox(where your filter sits) has two attached pieces hanging off the left side which are loosely integrated together. These are a box-like resonator compartment -that actually sticks back into the filter chamber- and the oval-shaped snorkel-looking tube that connects to both the resonator box and the main air intake chamber. To my topical point, anyone trying to get a more sporty intake sound and/or mild performance gains should remove these pieces from their intake assembly. After removing these components from my own car, I think this is an easy first step for people who want to get a bit more out of their Mirage without wasting money on dubious pipes and filters.
I notice there are several things happening when you remove these two pieces. First and foremost among them is that your engine is getting more air, more easily, than it previously did. This is most noticeable in the higher RPMs, when the MIVEC system engages the more aggressive cam profile. There is also substantially more intake/engine noise when this occurs, but it is surprisingly deep sounding and for those after a more sporty driving experience you will not be disappointed. The car pulls more easily to high RPMs, and sounds less strained in doing so.
The flip side of this increased breathing capacity, however, is that your intuitive feel of the throttle pedal is no longer correct, and must be re-learned if you don't want to drive your fuel economy numbers down into the 30s or perhaps even high 20s. The car breathes better -albeit more loudly- without these components, and if you're not attentive you'll be over-throttling it everywhere. In fact, this is what I think others have described as a sensation of lost torque at low RPMs. I think that, rather than there being any appreciable torque dip, what others are describing is their car bogging under an overly rich air/fuel mixture and gearing combination. When I want to get good fuel economy I drive gently and coast when I'm able, and I still regularly get mid-40s MPG even without the two pieces mentioned above.
I encourage anyone with a 10mm socket and some curiosity to try removing these pieces for themselves. The car will run just as good as it did with them attached, and you may find you like the MIVEC noises.