A year ago I have measured the difference between the stock airbox and the GTA intake.
I have measured the stock setting on my 2.0 JTS and I have swapped the resonator box for the GTA intake and measured the difference in airflow.
See also some diagrams I have made after the first 6 runs with the stock airbox.
The second diagram is all the data of 6 runs plotted in 1 diagram (STOCK), it can be seen it lacks airflow at high RPM (from 5000+)Volumetric efficientie drops from 95% to 85% [:^(]
The diagram below represents the data measured from the first run only (of in total 6).
OKAY THE VERDICT:
I doubt if it if any power is gained, it could be that it had become worse especially in the mid range @3750 en @4500.
See the links of the diagrams.
COMBINATION OF BOTH PLOTS
The influence of the outside temperature can be neglected, it was even cooler by a few degrees during the GTA intage runs.
The outside temperature was approx. 27-30 graden on both runs.
NOTE that I do not know where the outside temperature is measured. All I know is that it is refered to as the inlet temperature by the EOBD.
I guess that it is measured in the MAF. This does not mean that the air which flows through the inlet has this temperature.
The outside temperature was lower than the measured inlet temperature.
As the inlet is heated by the engine, it is cooled by the incoming airflow. An equilibrium wil form, but I consider it unlikely that the incoming air will be equal to the measured temperature.
Anyway the shorter the inlet duct the less the entering air wil heat up as it doen not need to cool down the coplete inlet duct. Therefore in theory the much shorter GTA inlet has the best opportunity to keep the air cool.
My verdict: a nice placebo part wich does not give any power increase but gives you a better sound from your engine which gives you the impression you did gain some power...