You said 60psi @ pump but what flow rate? Measure at rail and observe when WOT. If drops it almost always means pump is at fault. Pump needs to supply >60 psi I think. It needs to send about 15-18psi back to the left tank plus 50 to engine. (at volume).

It points to the pump at fault.

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2011 E70 • N55 (me)
2012 E70 • N63 (wife)