95/96, 850 2.0 T5, startup, rattling, power loss

[fapers]

Hello,
In the past month for 3 times I’ve experienced problems with engine start (starter turned properly and I could hear fuel pump working). Yesterday however, I noticed that during full acceleration – at higher revs, engine suddenly loses a bit of power and at the same time you can feel kind of rattling or vibration in the engine. After letting off the gas pedal everything goes back to normal ... Besides, everything seems to be normal. Lambda control light does not light up indicating any errors. However I get a faulty knock sensor code 1-4-3. To my intuition the problem is with the ignition (but approx. 2 years ago I replaced distributor cap + rotor and the plugs + ignition wires were replaced about 3 years ago) or the amount of fuel in the mixture, but that could be caused by many things. Maybe someone experienced a similar problem and could suggest what to begin troubleshooting with?
Thanks in advance and best regards.