similar issues christophe, in neutral or first will rev out no problem pretty much, higher the gear, worse it gets.
Fuel filter is brand new which has helped a bit, the old one looked OE, seems to be getting better sometimes, but sometimes not....I think Ill check the wiring for the pump underneath the car as a lot of the connectors under bonnet were loose / dirty inside. Could be the pump isnt connecting properly and isn't getting the right voltage? Would explain why its near normal some days and other days its a pain to rev.