Hi again

How is the fuel pressure regulated?

What fuel system is this?

Can you scope the pressure control and see if there is any relationship with the fluctuations?

Is there any fault codes?

Sorry for all the questions

If you are willing to scope n post we are all willing to learn.

Also where did you have the ground lead for channel A?
If you decide to scope just the FRPS, if you use the sensor ground you will get a near perfect waveform with no noise.

Cheers
James

EDIT :
Just so you know if you are using more than one channel On your scope NEVER use sensor ground as your ground reference!!