All,
I'm back.  Been away too long.  Lots of catching up to do.

The problem: My  )&$^^$#  Lyc IO-360 went south again.  Blew a head.  Fixed it for something over $2k.  Still have a power loss (down to about 60%) about 5-7 min into every flight.  After extensive trouble shooting (checking everything but fuel pressure which I don't have /yet/) I'm pretty sure it's fuel [delivery] related.  My 26 psi electric boost pump costs $600 at Spruce.  The Engine driven pump is $225.  I believe they're both bad. I need:
An automotive replacement for the electric boost pump.  John Slade said IIRC that his pumps set him back about $85 each.  I would need to plumb a return to the sump tank (or back into the inlet) side of the pump) through a pressure regulator that I could set at 25-27 psi.

Does anyone know of a fuel injection rail regulator (or anything at all that can be plumbed into an AN-6 system) that can be adjusted down to regulate at 26 psi?

Do automotive high pressure fuel pumps allow fuel to pass freely if they are turned off?  Like, could one plumb two of them in series and use them one at a time (as that's what would have to be the case if I were to retain the engine driven pump)?  If so, what might be the pressure drop across the idle boost pump when the engine driven pump is carrying the load and the boost pump is off?

What are anyone's thoughts around dispensing with the engine driven pump and using two electric pumps in parallel?  This idea just popped into my head as I was writing this, so it's still in the "brain fart" stage.

Thanks in advance for any and all ideas ... Jim S.