Car is jerking violently between 2,000 and 3,000 RPM's

Hi, I have no more ideas as to what could be the cause of this. I inspected fuel pump with a pressure gauge and it pumped at healthy 2.5 bar (although it was measured while the car was stationary). I replaced the spark plugs the ignition wires even an O2 sensor and it still is jerking. I thought I might be clogged fuel filter, so I ordered a really nice one from Bosh and cut open the old one by Kamoka that I had put in there four months ago. It was not black or anything. Only suspicious thing I have noticed is that the rubber top of the filter itself was quite dissolved. And since I am currently replacing clutch I cannot test the new fuel filter. Do you have any recommendations as to what might cause this jerking? I would suppose it might have something to do with fuel and/or spark but I am not sure. I would appreciate any help. Thank you