hold on....before you jump up and buy it....
what are your plans with your GSR? N/A? Turbo?
Skunk2 is good for N/A, and know that it is simply a re-ported ITR manifold replica so the coolant ports in the head and manifold line up (ITR manifold wont line up to the C1 head correctly).
JG & VENOM manifolds are good for Turbo or supercharging (if you use the Vortech supercharger, NOT jackson racing!) because of their better ability to hold more volume of air and wider/shorter runners.