| A company in Germany were making airtubes when I did some research about a year go, in their kit you got what I can only describe as a colostomy bag to replace the OE item, under the front subframe is where it would go according to them.
They advised performance gains but only at very high speeds when the ram air was really doing somehing and the increased csa of their items could be utilised to the max.
You have also lost the little tubes which are molded into the originals at 90deg to the airflow and control the sound waves and airbox resonnance.
There was quite a long thread about this relating to the 999/749 range at the time with some interesting info.
Helmholtz resonators seems to ring a bell |