Yes it sits in the engine compartment but I suspect it makes little difference. I think flow is probably more important than filter location. All the Japanese tuner cars putting out over 300 hp have filters mounted underhood. If I had a local AWD dyno, I'd run some tests. Unfortunately that is not the case.
Blitz intake WAY outflows the K&N filter. It's actually a really nice kit. I got the Injen cold air because it was available first but I think I would have used the Blitz had it been available back then. Maybe I'll switch later on.
i have seen the blitz on a guys wagon. he told me he likes the sound and he said he can feel more in the midrange torque. not too much more compared to the stock with the k&n or an itg. the inlet pipe that goes to the intercooler is whats goin to make a more noticable difference. i have emailed bpm about theirs and im waiting on a response from them.
A higher flowing intake which is located in the Engine compartment (one that draws in hot air) will be less efficient then a slightly more restrictive intake drawing in colder air. Cooler air equals more HP. Why do you think we use an intercooler? Same purpose for a CAI, to make the intake air as dense as possible.
Hope this helps.
Yes temperatures matter somewhat but inlet to the turbo temperatures have less of an effect than temperatures of the air actually entering the motor (post intercoolr). I doubt that 10+ degrees of intake temperature difference will make moe than 2-3 degrees differnce in after turbo/pre intercooler temps and even less of an effect after intercooling.
They just tested in the newest Super Street? I'm not sure becuase I get all kinds of magazines... anyways I think they got a 11-12HP gain from the filter alone. The filter itself retails at around $220 though but you get about 2-3 times the HP gain compared to K&N.