The AEM Intake that is made for the iA has a definite HP gain, though small. I wanted more sound from my engine (especially for shifting), and this helped with it. I feel more torque slightly.
I know opinions aren't fact and everyone tends to base claims off their imagination (placebo as you say)
So here's a helpful fact:
Prior to AEM Intake. Cruise control set to 59 MPH, in 6th gear.
I would drop 3-5 MPH on light grade uphill every day to work.
After the intake, no change in speed, no need to downshift.
Thats a fact.
So, while I may feel a little more kick, and definitely needed the audible engine...
this has been where I have seen the small HP increase.
Now, is that worth the money? For me yes, but others.... may not.