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Since it's a cpi do you have a return line back to tank?
cause weather the pump produces 115psi or 65psi you should by-pass unused fuel, If you suspect back preassure check that return line & the reliefe spring, if it's clear you have a defective pump.
Sounds like Thier trying to get out of a warranty claim.
If you don't have a return line you need one.

Good luck.

have a return line & vent line also
I'm wondering if a pump putting out to much pressure can be a problem?