Well, perhaps you forgot to turn on the No Smoking sign?
It appears that you’re referring to the new “Particle Effect”. This new visual effect is arguably a bit exaggerated. There is a way to disable it, but the way I know is via PlaneMaker.exe. If you know the basics of using this included X-Plane application, the feature is under the following section for each airplane...
Dropdown menu: Expert | Invisible Parts.
At the bottom section, uncheck “Built-in wing heat effects”