I think if you do a search, you'll find that most people are very happy with their evolutions. They're made in the same factory in China as the Magnum engines. The carb, for example, is identical for the 2-stroke Magnum and the evolution.

I have an Evolution .455 trainer system on my H9 Arrow. I must be one of the few whom got a lemmon, because from the start the engine would rattle, produce a lot of sooth etc. After about 5-6 gallons of fuel I sent it back to Horizon for repair. They completely rebuilt the engine under warrenty. I broke it in according to DarZeelon's instructions and ever since the engine has been a real performer. Oh, the muffler IMO is a POS. I changed it out and now I'm using the Tower muffler. Much better.

-tycho