bunker__
Hey Hristo,

not sure if that answers your question but you could try applying disturbance only on the outside of the smoke.
I find it easier to control that in a wrangle:

pseudo-code:
-keep voxels outside the smoke
-keep voxels that move fast enough
-create 1D noise (with divscale), if above thresold: create 3D noise
-add to vel

if(f@density<chf("density_threshold")){
    float speed = length(v@vel);
    if(speed>chf("speed_threshold")){
        // 1D noise
        vector hvec = (v@P +  chf("divscale"))/chf("divscale");
        float r1 = float(random(hvec+@Frame+chf("seed")));
        if(r1>chf("noise_threshold")){
            // 3D noise
            vector hvec2 = (v@P +  chf("divscale"))/chf("divscale");
            vector r3 = (random(hvec2+@Frame+123+chf("seed")))*vector(2)-1;
            v@vel += r3 * speed * chf("disturbance_amount");
        }
    }
}

The noises are really basic and quick to compute, just cubes, no smoothing...
Also that way, I'm only adding noise to some percentage of the voxels
eg: if noise_threshold=0.99, only add noise to 1% of the voxels.
it looks a lot more natural, not just adding noise everywhere
... and you can adapt the code to use any mask easily too!
example attached, hope that helps

vector disturb = random_brj(@P,int(@Frame)+12312);
disturb = fit(disturb,{0,0,0},{1,1,1},{-1,-1,-1},{1,1,1});
float distrib = random_brj(@P,int(@Frame)+14545);
distrib = chramp('distrib',distrib);
float mask = length(@vel)*distrib*ch('disturb');
@vel+=disturb*mask;