You'll lose a bit of bottom-end torque in favor of top-end power with the PP, and you'll essentially get roughly the same performance out of the GT40 and the Cobra. Personally, I'd go with the Cobra. I've heard too many bad stories about the fitment and quality of the PP, and Cobra's are easier to come by and cheaper than the GT40 (I'm assuming you are reffering to the tubular version, which is no longer produced). Or, better yet, get an explorer intake for even cheaper.