bcbigfoot... you might want to borrow some instruments from an airconditioning tech.... 20 minutes on the road and you'd have your info.
I have been using
Dwyer Magnehelic Gauges
for years. They will measure positive, negative or differential air pressures.
I even have one measuring the air through my furnace filter... one port to the room side of the filter... the other inside the duct. As the filter plugs the pressure change shows....I have the point to change the filter marked on the face of the magnehelic. They come in quite a few ranges...
I have a box full of them left over from past experiments...
Janet isn't going to like having them mounted on the dash of our truck. :M
I'll have to see if my iPhone has an app...
