I was looking at OS's very nice TR series, when I noticed they had a "Turbo" version with 1.3 HP. I know "turbo" has nothing to do with forced induction (I wish...

) and is some kind of glow plug. What exactly do these $8 plugs do for you, and is "turbo" really worth it?
I noticed the no-turbo (naturally aspirated?

) version has 1.1 or something like that. Good enough.