This is the easiest modification you can do... It takes less than 5 minutes, and it does result in a noticeable 'feeling' of faster response. I use the term in quotes because it has been debated as to whether or not it makes a difference. I believe it does. It is totally harmless to remove the resonator. Further, since it actually restricts the smooth flow of air to the intake when it's in place, removing it may actually prolong the life of your engine by allowing it to "breathe" more easily. And any slight difference in the air-fuel mix will be adjusted for by the ECU.
The intention of the resonator (and why it is called by that name) is to change the resonant frequency in the intake for a quieter sound. It has also been claimed to change the frequency of the intake 'pulse', which may actually be saying the same thing. While it's installed, it does exactly that - it make things quieter. Once you remove it, you'll notice the audible difference from the way it had been, and I think you'll also notice the difference in response. In the May '98 issue of Popular Mechanics, 'Care Care' column, writer Mike Allen identifies it as a "Helmholtz resonator to reduce intake air resonance at some engine speeds. It works by bouncing a pulse of air back into the intake path exactly 180 degrees out of phase with a noise pulse reflected by the closing intake valve." The article doesn't say what it does to the engine's horsepower.
I didn't dyno it, but my 'butt dyno' tells me the car IS 'peppier' by a scoche after removing the resonator; my logic tells me the same thing. Anything that interrupts the smooth movement of air along the intake path MUST slow it down, and slower movement of intake air robs you of power, although by only a small amount. But the whole idea of modifying a system is to squeeze every last iota of power out of what you've got. This is just one more 'iota' to squeeze out.
It seems to have more effect on the base (SOHC) models than on the DOHC's, (it's not applicable for turbos - there's no resonator), and yes, it is a noticeable boost in low-end power. There's also a slightly louder intake sound at WOT, which is totally logical, since that's the reason it's there in the first place-- to lower the pitch of the intake sound to make the car 'Stealthier'. All you need is a Phillips screwdriver, and there's really nothing to screw up, unless you forget to plug something back in... The concept is simple: below the intake hose, between the engine and the battery, is the resonator, which resembles a kind of squarish 'bottle'. Your mission, (should you choose to accept it), is to remove the bottle and plug up the hole it leaves, then reattach everything. Here's how...