Interesting thing I found dating back to 2002. Basically states that in addition to quieting the intake, resonators also produce power. Most of us know we add the z-tube purely for the sound and then gain nothing or even lose power but for uneducated people like me, this explains why. Complete with pictures!

http://www.planetsoarer.com/resonator/resonator.html

 

interesting

 

interesting but people have dynod the car with the G-Tube and Z-Tube with no power gains or losses when swapping the two.

 

I've been saying this for years, just because something looks restrictive doesn't necessarily mean that it is. You need to understand why the engineers made the part look the way it does. I use to be one of those people that thought intake resonators instantly means restriction. I did some research and realized that I was wrong for the most part. Most late model intakes are designed to reduce noise, improve throttle response, and improve power.

On 95-99 Maximas, removal of the resonator box closest to the throttle body will reduce power by up to 8whp in the mid range. These resonator boxes are actually Hemhotz resonators and they obviously improve power. http://www.freepatentsonline.com/6758304.html

There are also some intake tracts that were deliberately designed to choke the engine. My 94 Z28 was a prime example. In order to keep the Z28 from closely matching the acceleration of the same year Vette, GM added a significant restriction in the pipe between the throttle body and airbox. At one point in the tract, flow was impeded by over 50%. Adding a straight pipe in it's place instantly added 12whp/15wtq.

On the G, I ran the Z-tube for over 4 years. For giggles, I removed it one day and reinstalled the G-tube was a bit surprised to notice that the induction noise hardly changed and driveability/throttle response was the same, if not a little better. I sold the Z-tube. Tony at Motordyne has dynoed the G and Z tubes and there is no measureable power difference between the two.