A greater pipe length is needed, to be tuned for the lower RPM, the engine is capable of reaching on its own. -quote

So once I get this thing peaked out at its highest RPM, the pipe needs to be lengthened some more to keep it from going
lean in the air, right? Now, one more question, do I keep it at full length during break-in to keep it from leaning too much at that time? Or should I try to adjust it for max RPM fairly soon, and not run it too rich, since it's an ABC engine?
Thanks for your help! Ross