I've only had two engines in 10 years that have had any type of imbalance issue. One was cured with the simple addition of a reversed air scoop installed over the opening in the diaphragm plate. The other, an early BME 115 would not have mattered what the user did externally because there were design issues with the induction issues.

My feelings are that diaphragm carbs on two strokes, although generally quite adequate and generally effective, are just a little too slow in their reactin times to effectively compensate for changes in pressure. Those fooling with tuned exhausts have it a little more difficult. Most of our engines sound like they are a little unstable in various rpm bands that are otherwise steady in the trotlle input. From what I've experienced, injection will be the only way to completely stabilize power output in our little engines but it won't come cheap. Injected engines are rock solid in all rpm bands with absolutey no "wavering" like that found in carbuerated engines.

The mixture control solution you described would only be effective if the mixture required adjustment. That is typically not the case since once correctly tuned the Walbro and Tillotsen carbs have an extremely wide altitude operational range. What many may perceive to be an engine going lean on long uplines may in fact be a need to retard the timing from the advanced position it is in. As an engine loads up and heats up there are changes within the cylinder taking place (minor alterations in port timing due to changes in heating mixture densities and pressures) that are minimized, or eliminated, by retarding the timing until the temps and loads reduce a little. So we have a two fold problem to deal with, and most don't know about, or recognize, the second half of the problem. One thing is for certain, we will not be getting ignitions with a split timing curve from any of the current manufacturers. At least not at our price levels.