Evolutions run well when they run, and have the best throttle response I've ever seen on any engine. But their quality control sucks. At least they do service their products so they'll likely fix yours.

For future reference, any time you have an engine that is simply inconsistent, look for leaks. An engine that isn't leaking air and has good fuel and a good glow plug will respond very consistently to needle valve changes and will be fairly straightforward to tune. Blocked fuel passages from debris in the fuel or congealed castor will cause similar troubles. You may see issues like a fat midrange or frustrate yourself trying to get the lowest possible idle, but if everything is mechanically right the engine won't be inconsistent or unreliable.