Lots of things to check. Low mileage is a blessing and a curse as nothing has been done in terms of larger repairs.

I would start by checking CIS pressures with a CIS specific fuel pressure gauge and drive the vehicle at your RPM of concern to see if pressure drops in the lower chamber. This will indicate a fuel pump issue. Or one of your two external Bosch pumps are weak.

Again, lots of things to check but I think I would start there.