Alright here the I3 measurements :
as usual measured with my rig IEC711 clone coupler, run through apple dongle (USB type C variant), measure with REW, with sine sweep method. similar with Crin's.
Resonance peak couldn't be set exactly on 8khz on I3 because of large shell, the maximum fit i can get is nearly 7.5khz, not much differences in results though. Crin also couldn't get resonance peak set on 8khz. Don't worry that isn't big issue.
default Tri i3 L+R unit
filterless Tri i3 L+R unit
comparison between Default with cloth nylon filter VS filterless
the filter reducing high mids as expected, but only a little very subtle differences, but the side bad effect is bloated bass like similar cloth mesh used on other IEMs (BL03, Spring 1, H40) or maybe better way to say is "more bloated" compared to filterless, bad air flow is the culprit.
I did several mods to experiment :
dark blue : filterless
red : with micropore tape, covering 3/4 nozzle with the BA shaded by micropore tape (1/4 opening part is not above BA), note : there is a BA on the nozzle
green : default I3 with nylon cloth filter
tosca : small cut 5mm length of soft density sponge put into nozzle without covering BA, and then 3/4 micropore tape covering on nozzle end
purple : long cut 10mm length of soft density sponge put into nozzle without covering BA, no micropore at all
orange : long cut 10mm length of soft density sponge put into nozzle without covering BA, and then 3/4 micropore tape covering on nozzle end
Best tune is on tosca line, reducing high mids to be more balanced, but i notice there is a clarity reduction. No matter what, as i would to damper the 3khz protrude part, I can't do that, too much damper will reduce the 2khz more, so best so far is on red line, similar with default tuning, but more better texture, better bass tightness (no bloat), must resist the 3khz, you can just EQ the 3khz and 8khz a bit to your likeness and reducing bass also.
Hopefully this helps. Cheers!