I think the supply to the HP pump needs looking at. Tee in a vac/pressure gauge in the supply, anything more than 3-4inHg suction(cranking, 5inHg is ok at idle) indicates a restricted supply, then move the tee before the fuel filter and recheck if any restriction found.

Use the same gauge and tee I the return, up to 10psi is acceptable at idle ao cranking around 5psi would be my max gestimate.

If these prove ok then you have a bad hp pump.

Afaik your waveform looks like the imv is being controlled correctly. I am looking on my mobile so waveform not crystal clear but looks ok to me.