OK, all you aerodynamicists; here’s the scoop – what I did and what I
measured;
(Pressures measured in inches of water.)
1 – sealed the strake/wing crack in front of exit fairing - - No effect
2 – Installed Gurney flap at back edge of exit fairing (see photo 1) – Very
little effect.
3 – Set up manometer to get some pressures. (photo 2)
4 – Dynamic pressure in front of scoop, ½” from surface (photo 3) -- 9.5” at
160 mph.  Nothing wrong with that.  Free stream away from surface would be a
bit over 12”.
5 – Static pressure ½” from face of core – 3 ¼” (end of tube was pointing
slightly away from direction of flow at about 60 degrees to the flow; flow
velocity is pretty low)
6 – Static pressure just behind the core --- 0”
7 – Static pressure at behind exit fairing, ¾” from surface (photo 4)   – ¾”
8 - Installed VGs about 2 1/2 ft in front he exit fairing - No noticeable
effect.

So .. . plenty of dynamic pressure in front of scoop and only 3 ¼” pressure
in front of the cooler core.  This would suggest that the scoop/duct isn’t
working.

Photo 5 is a reasonably accurate x-section of the scoop and duct.  Shaping
was limited because duct entrance is right behind the spar, and by the
limited thickness of the wing root.  I'm just guessing that the somewhat
abrupt curvature of the upper wall at the entrance is causing flow
separation, turbulence; and whatever.

You'll also note in photo 4 that I had cut the center section of the exit
fairing to allow exit further forward - that didn't help.  I also did soap
drops on the surface which way air was going both in front of; on top of;
and behind the fairing.  In all places the flow was relatively straight
back.  I'm also guessing that there isn't much chance of developing a
greater negative pressure at the exit; but, hey, whatever works

All I need to know is a simple fix:-)

Al