Doesn't hurt to provide some additional fresh air to the DCIs.
http://performanceunlimited.com/cobr...n/ductfan.html
The smallest fan ( I have not purchased yet) will help with a delivery of 140 cfm. Again, it doesn't hurt to provide more fresh air, whether you "pump" it to the filters or allow ram-effect at speed. Increase of air mass is the power provider and the FMIC is in place to handle the real heat load.