STi guys - save me 11 million searches on NASOIC

[WRXtranceformed]

Yeah, I understand that they might not have benefits.

What I want to know is how they could possibly cause problems later on down the road. I just don't get it.

Subaru ECUs are extremely fine tuned to the stock airbox, and extremely fine tuned in general. They are unlike many cars in this aspect, in that the intake system has already been engineered for well over 300 horsepower at the wheels. Many aftermarket intakes change the velocity and / or entrance pattern of air into the intake which confuses the stock MAF sensor. This is why, with the stock ECU programming, adding the majority of aftermarket intakes onto the WRX/STI causes problems. Some people will tell you that they're using XXX intake and that they haven't had any problems, but guaranteed they have been running lean.

How can you fix this? Easy, get a custom tune. But, that would obviously be a colossal waste of money for just an intake. If you do more mods, such as a turboback exhaust and an intake, it might well be worth spending the money on a custom tune. I've heard really good things about the K&N Typhoon on the STI seeing some pretty good horsepower gains. The key is though, the ECU has to be reprogrammed or overridden because of the change in airflow from the intake.

Blow off valves are no problem, unless they were atmospheric, which is what most people do. At the worst they make you run very rich... I had a 100% atmospheric on my WRX and it stalled out at a stopsign because of it heh. At the very worst, on an STI, it will foul your spark plugs.

How can you fix this? Run a blow-through MAF setup like on my car (MAF sensor is after the blow off valve =p) Or, you can get an adjustable BOV like the Forge or GFB where you can set it to 75% recirculate 25% atmospheric. You would notice no difference really in performance.

Hope that helps.