I see. I am using errts files for processing (not doing GLTs) and did the @SSwarper first, so I feed those files to afni_proc. The issue is there are too many subjects and too many runs so using a different afni_proc.py for every run of every subject would mean too much work. If I can't find a way around though, I will use that method.

2^8 is, not important at this point but, suppose you have run 1, 2, ..., 8. You have two states of first run, it exists and it doesn't exist. Same for second one, third one, so if everything exist, you have 1 1 1 1 1 1 1, the last one doesn't exist: 1 1 1 1 1 1 0; second and fifth one doesn't exist: 1 0 1 1 0 1 1 1 etc. Two possibilities for every run: 2x2x2x2x2x2x2x2. I'm not sure the exact mathematical word for this is permutation or not (haven't seen maths in the last 10 or so years) but this is what I meant.

Best and thanks for the always fast and detailed reply,
Yasir