Particle System using distance emission stops emitting when script active..

I have a script that adds turbulence to particles and it works find for a time-based emission particle system, but If I switch the system to distance-based emission it doesn't emit. The relevant chunks of script:

 ParticleSystem ps = null;
 ParticleSystem.Particle[] particles;

 protected Generator noise = null;

 
 void Start () {

     if(noise == null) {
         noise = new PinkNoise(556);
     }

     ps = GetComponent<ParticleSystem>();
     
     particles = new ParticleSystem.Particle[ps.maxParticles];
 }
 
 void LateUpdate () {

     
     int ptotal = ps.GetParticles(particles);
     
     for(int i = 0; i < ptotal; i++) {
         Vector3 ppos = particles[i].position;
         
         particles[i].position += noiseMagick(); // Trust me, it works when using time based emission..
     }
     ps.SetParticles(particles, ptotal);
 }

I've searched google to no avail. Any clue what's happening?