This cold air intake (CAI) is a bit different than that’s currently on the market for the GR/GV STIs. What’s different? Your vehicle doesn’t need to be tuned for it to be used on your car, nor does it need to used with a Cobb AP OTS tune. In most cases, CAIs for Subarus are not plug-n-play. So when I saw the above URL posted within the IWSTI forums, I immediately had questions, such as ‘how did they do this?’.
Here is an engineering writeup of the product (by Mishimoto engineers). It is actually pretty thorough. Another cool fact is that it can still be protuned for further gains. Mishimoto claims,
The maximum gain achieved was about 25 hp and 24 tq at around 5300 rpm, with a peak gain of 12.7 hp and 2 tq. These results are very good for such an easy part to swap out. Increases on average through the power band measured around 20 hp and 18 tq, which would certainly be noticeable to the driver.
Additional notes regarding the air/fuel ratio of a car with this particular CAI:
The Mishimoto CAI follows the stock AFR as the car builds its boost. Once the engine reaches 4000 rpm the car is under full boost, as seen when the Mishimoto CAI starts to differ from the stock unit. The maximum AFR reached was about 11.7:1, but on average the Mishimoto CAI runs about 11.3:1 when under full boost. The stock AFR maxed out at about 11:1 and averaged about 10.5:1 when under full boost. These numbers were consistent throughout multiple runs, which assured the engineers that this CAI can be used every day without harming the engine.
Looks-wise, I like the Nameless Performance CAI better, even though that particular unit still needs a Cobb AP to be used (it can be used with any map that supports the AEM CAI). Pricing between the NP and Mishimoto CAIs are also very similar. The NP CAI is $299 and has an arsenal of color choices of the closeout and MAF housing. The Mishimoto CAI is $313 and only offers 3 colors of the intake piping.
I’m not sure which offers better gains on OTS tuning, but I don’t think you can go wrong with either solution.