As a precursor to an in-depth look at air intake setups I have begun recording under hood temperatures at different areas inside the GTI engine compartment.

Temperature at these locations is being recorded during daily driving activities, primarily a morning and afternoon commute lasting approximately 30 minutes.
Results from the Morning drive are shown in the chart below:

The results from the afternoon drive are shown on the next chart below:

Temperature at the filter and grill inlet becomes surprisingly high during slow speed and stopped conditions. Even when driving the filter location remains higher than the grill inlet location.