There are some common misconceptions in this thread of engine modding. Power and fuel economy can be had from modding an engine. IMO, if chrome on the sleeve has not been cut, then it isn't modded. All these little cuts in the brass of the sleeve are pretty, but they don't do a whole lot. Port timing and port shape is where it's at. Polishing IMO doesn't do a whole lot, and neither do all these coatings. To tell you the truth, you could only "see" the minute results on a dyno, and dyno's don't go down the track......(and that's a whole 'nother thread in its self).
Now being an engine modder myself, out of all the engine modders listed in this thread, I would recommend 2. I am associated with neither. EB mods and AB mods. Both of these guys can mod and do a fine job of "purpose" modding. Fuel, economy, smoother powerbands, etc.
FWIW, the RB C6 is a stout .21 and would make a fine truggy mill, but it will rip a buggy in half!
Now, you could have it modded and and have the power band moved up some to rid yourself of the brutal torque - and add to the top end. Then you have a race killer!
