Neither of those are the problem.
No, but the side by side 12" fans leave so much of the shroud open, I don't believe that's a problem.
See, that's the thing, and cavitation is a term I've used, but I am actually trying to describe poor or inefficient pump function, and THAT would absolutely be because the installer did not make sure the gap between the divider plate and impeller vanes was small enough.
In a 60 page long thread on the Pontiac Performance Years forum, the consensus is that gap has to be very very tight-1/10th of an inch, and the installer says Butler told him 1/16th to 1/8th, but the way he describes measuring it, and a few loose ends the car had, all causing major problems, has me doubtful that gap is as tight as it should be.
So my plan is to satisfy his concern that the fans and shroud are the problem, and if they are, well great. To test his theory, I'm removing the electric fans and shroud and putting the mechanical fan back on.
If that doesn't help, I'm going to hand him wrenches and watch him take all of the Wraptor system off to remove the water pump which is on the front of the timing chain cover, and then I'm going to see what kind of gap is there, and if unacceptable (which I think it is) I'm going to form that divider plate to where it is as close to the impeller as possible, and then put it all back together.