You must have an error somewhere else then, as my game runs fine with the file, and the smoke is gone. Tested it with the edits removed and the smoke is back. I suggest running a repair of DCS World and trying again.
Solved it.
In the file Mustang mentioned in "Config\Effects\ParticleSystem2\exhaustTrailAir.lua" lines 7 & 9 changed the values to 0, and the smoke was gone. Attached the modified file here if you want it. exhaustTrailAir.lua
Think of the training possibilities though, training combat maneuvers and being able to spectate from the rear seat. Or for formation aerobatics ride alongs (not your thing, I know).
No updates? Complain.
Updates? Not what I wanted to hear. Complain.
New FREE Aircraft: But it's not XYZ! Complain.
Why? It's purpose it to demonstrate the quality of the prop AFM. The fact that it happens to be a dual-controlled aircraft in real life is just a happenstance.
It will be a free aircraft for DCS World like the Su-25T is a free aircraft. Purpose is to introduce new users to the sim and the level of detail in the aircraft and flight models.
IF map SDK tools ever get released, you will, unless you want to sell anything you make as official content for the sim, that's where authorization, licensing, authorization etc comes in.