Fluctuations in fuel pressure sending me mad

Hi All
Need some help with fluctuating fuel pressure.
This is a all new dead head system and is in a Duster with new sender with 1/2 inch pick up, 1/2 to Holley 12-125gph pump, 1/2 to Holley 12-845 Billet reg and 1/2 to E85 Quick Fuel Q850.

Have great pressure from idle to about 3500rpm (6psi) and then it drops as low as zero and then back to 6psi.
After a run on the dyno it fluctuates at idle up to 5psi. Before and during the run float bowls are at the correct level.

I've rechecked the hardware and flow and pressure to the reg is great. Yes volts to pump are spot on.

This is starting to get to me as I can't find the fault