I can only speak of the tuned GRP .21 - amazing. Runs like a top engine should. Smooth idle, great response and the smoothest powerband I've ever seen from a .21 platform. Doesn't have that explosive surge of power, but more of a four stroke feel to it. Quite linear.
Current setup is with the GRP 2053 pipe and GRP #6 plug using Nitrotane fuel.
Paid $440 for the 'promo' pack, which came with everything above, minus fuel. (plus a pitmat, shims, decals, restrictors and nifty keyfob)