It's just the OEM 06/07 STi hood scoop splitter and rubber ducting/bellows from subarugenuineparts.com. I couldn't justify the price of the Zerosports splitter to Santa and I'm still running the stock WRX TMIC, so I figured the STi splitter might work a little better since its fitment was guaranteed (I installed it this morning and it fit perfectly) and it has a little rubber piece to help direct air all the way to the TMIC. I originally thought I could reuse the rubber ducting from my WRX splitterless piece, but I couldn't because the STi splitter is a little bigger and the rubber is slightly bigger (length-wise) to accomodate that (however, I did have to reuse the plastic clips to hold the rubber on to the splitter and the screws and clip to hold the assembly in the scoop). Height-wise (distance from the bottom of the hood to the top of the TMIC), they're the same. I thought maybe the STi splitter rubber ducting was shorter in that regard because I assumed the stock STi TMIC was thicker and protruded significantly more toward the hood, but that's not the case.
The 06/07 stock STi splitter is still quite obviously not designed for my application as the affected cooling area appears to be about 1/4 to 1/3 larger - reaching back toward the firewall a little more to accomodate the larger stock STi TMIC. Side to side, it's about the same. It appears as though half of the air (top half, closest to the firewall) will actually be directed mostly at the black plastic part of my stock WRX TMIC, so that's pretty useless. But the other half of the air (bottom half, closest to the front of the car) will be directed more toward the middle and front of my stock WRX TMIC, so that will hopefully be slightly more efficient than the stock WRX splitterless piece I used to have.
I've created a nifty little illustration for everyone's viewing pleasure. The yellow lines indicate about where the rubber ducting meets both TMICs and about where the splitters end at the TMICs.
From top to bottom:
1. Stock 06/07 WRX TMIC w/ stock 06/07 WRX splitterless piece
2. Stock 06/07 WRX TMIC w/ stock 06/07 STi splitter
3. Stock 06/07 STi TMIC w/ stock 06/07 STi splitter
I'm just hoping this setup will be slightly more efficient than my stock splitterless setup was. Even though I might have to upgrade again to a Zerosports (or other) splitter if I get a massive TMIC in the future, I can try to sell this one and make a few bucks and hopefully it won't be a complete loss.
Plugs are NGK Iridium LFR6AIX (stock heat range).