Most car have genuine petrol filters in the petrol fuelling tank, the pipe where the nozzle is inserted, sometimes it is hard to see it because it is bendy(from fuel cap to petrol tank) and i would make sure it is cleaned! Maybe something is blocking it, leaving it 20-50 % open.
Almost same way when you leave hair in the sink, and water stays, but drains slooooowly.
Good luck