247islander

I have a 2009 Tahoe flex fuel 5.3. I have recently changed the fuel pump. I’m now having trouble with it starting after running and then shutting it off for a short period. I checked fuel pressure at the rail and is within specs. When I turn off the ignition the pressure gradually increases from mid 50s psi to 75 and then eventually drops slowly after 40 minutes or so. Is this Normal? Fuel pressure is built into the pump and I’m thinking my vehicle doesn’t like the new “Carter” pump. Any insight here?