i used the one from HPF on my SP61GT and noticed huge difference in intake temps. in the fall when the outside temp was around 75F, it dropped the underhood intake temp an average of 18F. in the winter, its dropped the underhood intake temps and average of 20F. the only thing is that i get paranoid after driving the car since i dont have a turbo timer, so i idle a few minutes before shutting the car off.
-pete