EW10J4 running rough, misfires under heavy throttle

I bought peugeot 406 2.0 16v petrol EW10J4 RFN that was supposed to run with only 3 cylinders when cold. Previous fixes done: injector 3 (counted from belt) coil pack, spark plugs. When i bought the car, i could not get it running on 3 cylinders as it was already warmed up. Drove the car home, and noticed that the engine cuts out when pressing roughly on throttle. The engine misfires and then picks up again. This happens mostly at over 3k rpm and with over half throttle, especially when pedal is pressed quickly to the floor. This also triggers antipollution system faulty message, and injector faulty messages. There is no logic which injector is faulty which time. I also had O2 sensor heater fault, but i fixed that with used O2 sensor from 307. Error did not come back but nothing changed. The engine shakes a little when cold, but nowhere near like one cylinder could be missing. Warm engine idles perfectly. I am now suspecting stuck tappets since that seems to be common issue with this engine