Just kind of making up a generic example. And the comment about the tuned pipe also refered to the articles on unloading in the air. I don't believe the particular reviewer did anything with any performance engines, just the normal run-of-the-mill sport engines most people would use. I also never read a full fledged review on any of the full race engines used for competition free flight or control line speed like .15s that top 40000 rpm, or one control line .65 that had been tacked on dynos at over 28000 rpm. High power, but totally unuseable for any sport RC flying.