As per this thread here, some great information posted up by Tim Duncan from http://ghettogarage.org/
This is on a beams motor, so the overall intake runner length is not directly comparable to a blacktop engine.
BUT it is very interesting to see how the change in trumpet length basically shifts the whole curve (especially the dip) up and down the rpm range.
Especially so, since theoretically a longer tube should give a lower rpm at which they are beneficial...
However I guess that's explained by the longest trumpets of the lot are just on the verge of using perhaps the 2nd or 3rd reflection, lower rpm using the 4th or 5th perhaps.
My previous workings showed that 110mm trumpets would be beneficial from 5-8000rpm, and shorter trumpets dont start working until a higher rpm. So it's interesting to see that this somewhat correlates.
I've never seen such a thorough back to back test of different ram tube lengths, for any quad throttle setup.