I don't know where this idea of running the bottom end rich got started, but I find it a bit humorous. It needs to be tuned correctly. Obviously there is a window where the engine will run but perform differently, but if it is rich then it needs to be leaned out until it is properly tuned.

When you guys say the bottom end needs to be rich, how long will your engine idle? Assume the engine is at operating temp etc.... If your engine loads up and dies relatively quickly, then it is too rich. If it doesn't load and die quickly then it isn't rich, its tuned properly.

They way you guys put it, you need to mistune the bottom end for it to be tuned correctly, which is a contradiction.