are you searching for this?
If you have a fuelpressure drop at high rpms, I would check first if you have the same voltage at the pump as on 5000 rpm... at what psi/bar did you set your fpr?
are the smal pressurehose between the fpr and the sensor o.k, sensor and the rest?
you should defently have enough fuel for your setup with a stockpump. perhaps is your pump bad or some of the sensor make a restricton at the top end...... It's hard to say without having the car next to me.