Trying to go through everything here.
Fuel Pressure regulator
Low voltage wires to relaybase of fuel pump relay
Dirty fuel injectors
Badly reading O2 sensor.
Now, I have no ECU warning lights come on and no codes stored. But could the o2 sensor be sending a bad reading to the ECU? It's strange cause at RR day, bad readings were after about 3k rpm, which is where the o2 sensor becomes closed loop and the ECU takes no readings from it. So not sure this could be the fault. But at idle it was tested today and although they only did a BET on it, it failed that. So I'm assuming it's underfueling and pumping out too many hydrocarbons. So still a grey area to explore.
Fuel filter has been replaced, so have plugs, inlet has been cleaned and FPR replaced. Shall be fitting another pump next week to see if that works.
Have a slight fault with the wires to the fuel pump relay base. Somewhere along the line there is a break in one of the wires which will shut the relay off, happens very very rarely. Now if you wiggle it about it'll be fine. But if there's a break in the wire then this would give a lower voltage to the fuel pump or would it only be interfereing with the relay?
Injectors I'm not sure about as the engine is low milage, not sure that that makes much difference to them getting dirty. Or if it would effect an emissions reading to the level I'm gettting.
Does anyone else have any other ideas?