Anemometer
 

As usual, I was looking for something else when I came across this:

https://cdn.thingiverse.com/renders/...w_featured.jpg
www.thingiverse.com/thing:756489 -- printable Anemometer

I don't know how well calibrtated this is, but they would be cheap enough one could put them all over a car.

An obvious remix to turn the flat plate arm 90 degrees and add an airfoil cross section.

And a swivel base for the sides.

Technically it doesn't have to be accurate, just repeatable. Tuft the vehicle, find flow anomalies and see if they are higher or lower pressure