Dear @lukpblr,
Unfortunately, HEHAD-EQ and THNEU-EQ can only be used for scoring purposes and not as source particles.
I would suggest to have a look at the lecture on electromagnetic production and transport thresholds and to the biasing lecture from the last FLUKA course.
From the first one, you could see that probably you could increase the thresholds and then reduce the time spent transporting the electromagnetic component which is not relevant for your problem.
From the latter, you could learn how to “enhance” the components (hadrons and neutrons) you are interested in.