I've met and played with a few of the Evolution glow engines over the last couple of years. The only thing I've seen with them that has been a problem is the fuel line between the remote needle valve and the carb. For some reason most have had a hole in that line out of the box. The only other issue I have seen with them has been due to the owners and over aggressively turning all the needles.

BTW, the OS line of engines ain't all they used to be. OTH, Saito is better than they ever were.