(Assuming MAF is ok/nothing was damaged during engine bay wash)
If the pump is on its way out it will still make fuel pressure at idle just fine but will not be able to keep up under full load/high rpm.
You may just have a tired pump and or dirty fuel filters. You can check by logging a
fuel pressure sensor or monitoring a gauge through a WOT pull. *Fuel pressure should rise/fall 1:1 with boost\manifold pressure.