There are a few differences between the two. I had the INJEN originally.
Most noticable, the crankcase vent tube is BEHIND the MAF on the F5 Fujita, where as the INJEN, it is in front. And depending how much oil is being vented, this may or may not have caused CELs before.
Also, the bends are tad bit more subtle on the F5 and I didnt have to clean the polishing residue from inside the the F5.
The air filter design has already been mentioned, and on a side note, the workers have a special polishing powder on there hands when packaging the intakes, thus the absence of finger prints on the intake when you removed it from its packaging.
It is also worth mentioning that the Weapon*R/MMW intake is nice also.