RE: Smoke system on an O.S 91FX
Very possible, but skip the heating coil inside the muffler - it just robs the heat that you so desperately need.
Here's some great info on how and WHY smoke systems work - including the easy-to-make home made smoke system that I use:
[link=http://www.rcuniverse.com/magazine/article_display.cfm?article_id=455]Got Smoke?[/link]