DragonSol....Great questions.
1.) Yes, the stock 260 HP of the GXP is crank. At the wheels, the stock GXP will show around 210 HP at the wheels. That number will vary a little.
My numbers from the dyno are wheel HP. To throw a bit of a curveball at you...That dyn run was performed before and after I installed the SOLO high flow cat. So, I am sure the numbers are a bit higher now that my car has had time to learn the new mod.
2.) Different dyno's will produce different numbers. So, numbers will very. But, as you can see...with my mods using a dynojet dyno...I am getting 265 at the wheels.
One other thing here...I am not much of a HP nut. But I love my torque and getting 336 is huge! That is a BIG plus with the Wester's Race tune. When you get yours...that will be the main reason for the smile you cannot get off of your face.

Enjoy your new tune. It is a huge mod for the price.