Hey gang!

I'm having a simple but annoying issue, when trying to keep a steady RPM with my foot on the gas, in neutral and stopped (cannot drive it at the moment), the rpm bounces steadily in a variation of about 200rpm. Sounds like a iacv issus but less dramatic. No throttle imput, idle rpm is steady.
Engine is a H23 vtec obd1 (tuned). It was running fine for the last years. It still runs fine but i found this annoyance recently.

I tought of a bad TPS sensor (glitchy reading?), but i replaced it recently and calibrated it. I do not have the equipment to test it with an oscilloscope.

Anyone would have a clue of what to look out for?
Made a quick video to help visualise;


Thanks!