Because it wasn't consistent and further testing w/o the sensor still shows low pressure and bubbles.
I'm now down to:
1) Fuel tank pickup/screen
2) Line from tank to selector valve
3) Selector valve

Marv's post now make it seem likely that it could be the selector valve.
Hopefully I'll get the last testing done today.

Finn

Tracy Crook wrote:

Removed flow sensor and filter and amount of bubbles appeared to be
significantly less. Put sensor back in, and bubbles reappeared,
 

Finn, why did this leave you baffled?  Sometimes the obvious answer is the right one.

Tracy