HP gains would fluctuate too much based on ambient and underhood temps. The easiest test to prove the effectiveness of this product is a simple temp reading of the top of the intake manifold (and if possible the chairge air) before and after the install with the car in motion and the motor at operating temp. Use the temp delta to speculate your own HP gains.

Personally I view this as an additional mod. CAI + EGR and air pump blockoffs + phenolic spacers = the coolest charge air temp you can expect in a Crossfire.