Hi!
You don't set a glow engine by djudging what the exhaust vapor trail looks like, this seems to be a missunderstanding many newcomers! You set an engine by ear! And you set it slightly rich! Any vapor trail or not is not important ,though, there will be considerably more fuel vapor coming out of the exhasut from engine set rich than from an engine set lean...
Setting engines by ear is how racers set there engines and how experienced sportfliers set their engines.