Well, an air splitter would benefit even a stock tmic. It has to do with the fact that when you're driving, most of the air coming in the scoop hits the top half (closest to the firewall) of the intercooler and the bottom half (closest to the front of the car) barely gets any air. By diverting some air toward the front, the tmic would be able to cool air more efficiently and, ultimately, improve power a little. It's a pretty good concept and testing has shown it works - regardless if you buy a pre-fabbed piece or do a diy mod.
07 WRX (Albins 5MT + Blouch 20G)
Jorge Carrillo Tuned (365 whp/340 wtq)