Intake tuning is not as important as exhaust tuning, but it does have an effect. From another forum:
Here is some info to help with the issue of what harmonic reflection is being used in an intake - use this formula to see what is happening.
In most cases the primary reflection is way to long to fit into any bike/ski etc ,but tuning to the second is sometimes possible but has a lesser effect over a narrower range.
The third reflection is usually the most doable, but again has less effect than a second harmonic.
RPM = 108K ( 1st hamonic ) 97K ( 2nd harmonic ) 54K ( 3rd harmonic ) / L ( inches )
So examples are 1st Harmonic 6000 rpm = 18",and 12,000 rpm = 9"
2nd Harmonic 6000 rpm = 16.16" and 12,000 rpm = 8.08"
3rd Harmonic 6000 rpm = 9" and 12,000 rpm = 4.5"
You can juggle the reflection number as well as tune for peak torque or tune for peak rpm, all depends upon the end use and the room available.
So for a bike needing intake tuning at 9000, the choice would have to be 3rd harmonic at 6.75" or going to the second would be near 12" so no way would that fit I would imagine.
Lohring Miller