There seem to be some issues with the Input Particle. One thing that is, perhaps by design, but unfortunate if so…is that prtVolume and prtFFX will not read directly into the particle source input. Also, if you read PFlow in, it works, however you get the issue where it only updates if you manually hit update, Auto seems to have no effect. I think I am still on beta 2 so I will update and re-check just to be sure. But this Nearest Particle query is great 
Can you explain step by step what you are doing? I have no idea what you are talking about.
PFlow is not supported as particle source yet, as far as I know. What do you mean it works when you update manually?
PRT Volume and all PRT objects should work, as long as there is no dependency on the Genome modifier. So if you added a Genome to the mesh that the PRT Volume is made from, it might reject the input if it causes a circular dependency. If you see an input node pick an object and when you reselect the node the object is gone, you have a situation like that.
I just tested by crating a Plane, turning it to PRT Volume, the created a Teapot with Genome on it and used NearestParticle to squash the Teapot to the particles on the PRT Volume plane. It worked as expected. I don’t have FumeFX so I cannot tell what PRT FumeFX does, but it should be the same situation.
Make sure there are no dependencies between the object with the Genome and the object the Genome is referencing.
ah…I didnt think of the dependency 
Cool. The only issue with PFlow is that the Genome modifier will not update by itself, same as how the maxscript function worked. Every time I manually hit Update, it updated correctly, moving the time slider did not, even with Auto update enabled…but if it is not yet supported…not a big deal. 
Can you explain what the Genome does and how it uses the PFlow?
Some screenshots would probably help.
hmm well apparently it was a fluke that I thought it worked. I was emitting a small stream of particles near the pivot and I was getting an effect at the center of my mesh (right where the particles were). But now I am getting multiple effects where there are no particles and when I spread out particle emission, the effects are only centered on the Y axis and not what it should be… So, definitely doesn’t work 
WIll it?
anyway here is a scene just in case you are still interested.
gnmParticles-PF_001.zip (19.6 KB)