just read this and i was thinking high pressure pump, was going to ask if its noisy? if its not generally there ok but you have done right to fit in tank pump , as a rule this is the one to go 1st then kills the HP pump in time
My next thought was have you checked your fuel pressure, this can cause alsorts of problems, then i was going to say about the little banjo filter but you got there before me lol, but i would get the fuel pressure tested, my car was a nightmare till i did this, better starting and generally running great, you can make a fuel test kit for under 30 quid and well woth keeping around