Pre heat coils are for glow technology. Glow engines run cold. Gas engines run MUCH hotter, which is where a lot of converts from glow run into trouble.

All you need is an oil injection source close to the exhaust opening for a gas engine to have an effective smoke muffler. Been saying this for years but people keep spending a lot of extra money for glow style smoke mufflers. Slimline has to love newbies to gassers.