Fuel pressure mystery

Acted on advice  - removed fuel pressure sensor, (attached hose full of fuel)  washed/squireted as per Roger technique.

Reinstalled in slightly higher position (limited firewall height in a Sonex) and possibly more importantly have sensor vertical against firewall.

1.5hrs flight - fuel pressures AT ALL TIMES GOOD!!! - this includes when switching off Boost pump - much less drop.

My heartfelt thanks to all advisors.