Misfiring in cylinder three?

It started 2 weeks ago driving on highway I started losing power. I parked car and connected the diagnostic tool it showed four codes. P0001, P0300, P0301 and P0303. I read that changing oil would most times take care of VVT solenoid code, and it did. Replaced two spark plugs in one and three cylinders fixed first cylinder but misfire in third piston stayed. From the start I could feel the car vibrating and shuddering when I was getting off the freeway. That was still there when idling, also after replacing the ignition coil and the electric plug it seemed to get better. It actually smooths out now when I'm accelerating, rough idling is still there and sometimes when I accelerate, I can feel the pedal isn't giving the engine power instead it starts rattling badly (only when engine is cold). So, that's why I think it's my fuel injectors need replacing. But it could be my catalytic which I replaced a couple months ago. I'm not sure if I did something wrong but the car was working fine until that day. Hope it's enough to get an answer, it could be so many things causing it that I'm not sure where to start.