Hey Jim, I have the same cooler and in the same spot. It was in front of the radiator and I was getting high water temps so I moved it. I've got a 2 hole duct in the turn signal hole and 1 hole duct in the fog light hole with brake duct hoses going to the cooler. I was worried about the air stacking up behind it also and considered maybe cutting the wheel well or louvering it or even building some ducting to dump the air on the header somehow but my oil temp gauge says I'm running cool. This weekend at Sears point I didn't break 180 and considered covering one of the ducts, and last month when it was near triple digits I ran at 200 degrees.
You were at the same events so the only difference I can think of is that I drive ON the track, whereas you drive OFF the track. I know when I'm behind you I usually get at least one dirt and rock shower a lap so maybe your cooler is full of the same dirt? I guess what I'm saying is maybe it's "pilot error"
