1991 ZR1 engine knocking on idle

[evski]

Hi, after almost 3 months shipping in a container the engine started knocking on idle. I assume it's misfire so clutch cnocking is just a result of it. About my car:
-43k miles
-Haibeck chip
-FIC injectors, coils, plug wires and plugs replaced in 2011
-injector resistance on cold engine 15.2 +/-0.2 ohm.
-replaced clutch
-fuel pressure before start goes to about 50 psi (I wasn't able to check FP on idle because I bought the cheapest tester. I'll try to fix it and check FP on a working engine)

Now my plan is to change plugs, because that's the only thing I can do by myself before going to service. Maybe O2 sensor? I also purchased LiquiMoly Injector Reiniger. I read that could solve the knocking problem.

https://youtu.be/MhHxa_B8J8w idle sound
https://youtube.com/shorts/1snaGeQkXD4?feature=share

I will appreciate all your inputs.