-SOLVED-ish-
After installing this mod (and Stock Waterfall Effects), there are no rocket plumes whatsoever. I first tested this on the R.A.P.I.E.R. engine, as it has a liquid fuel and air breathing toggle, and neither worked. I did notice that on the air breathing version, there were little puffs of air coming out every once in a while. I also have infinite fuel on to make sure that it wasn't just me not supplying fuel to my engine.
I'm using Stock Waterfall Effects 0.5.1 and Waterfall 0.6.7, in case that helps at all.
Solution: I had either Near Future Propulsion and/or Far Future Technologies installed too, and I think if you have those installed too (without the mods to make it work) it turns off all trails. My solution was to delete the GameData folder and tell Steam to reinstall the game. Then, I added Waterfall and the stock effects mod and it works now.
