I have found the fans to move the air the best when they are further out of the shroud than half way in. I run mine at only .375 inch in the shroud with all the rest out. By moving from half way in to the further out, I improved my idle temp by 20 degrees.

If that doesn't work, you may want to switch to an AC (small impeller) pump and AC pulleys (1.3 ratio). That will almost certainly cure the problem.