I'd like to offer that in every instance we've had related to us of a Hahn-equipped 2.4 car facing off against a stock GXP, the Hahn car is the clear victor.
Now, once the Hahn-equipped GXP's are more prevalent, this will obviously change.

But for the comparo basis of the standard 2.4 with Hahn Stage II Turbo against a standard GXP, the question's been answered.
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Bill Hahn Jr., Hahn RaceCraft, Inc.
Home of the World's Quickest and Most Powerful Solstices
First to the 14's, 13's, and 12's in the 1/4 Mile
12.00 @ 117 MPH Street Solstice World Record
Hahn RaceCraft, Inc.
Turbocharging GM's since 1988
http://www.turbosystem.com