According to this chart the factory only overdrove the pulleys for a/c & C.A.P cars.
Is that to move water faster or spin the compressor faster ? Remember these engine idled at pretty low rpms stock.
Also notice that trailer tow pkgs underdrove the pump.....
It would be interesting to see what happens if you were to try underdriving the pulleys since you already have a baseline.
I agree that the pusher fans are not doing you any favors especially when off.
Other variables such as....is the car properly tuned ? Was the cam degreed ? Is the block bored to the max ?
May be the issue...
