Sounds like a injector is bleeding off on hot soak. Not all that unusual. You can pull the injectors and take 'em to someone who has a bench tester for testing. (and sometimes you can fix 'em this way as well, blows the trash out)
I've run into a few slightly leaking fuel pump check valves doing this as well, but that is normally accompanied by a hard start on hot soak, some black smoke and skipping on start.44K is a great product but, 40psi is not enough to dislodge the trash most of the time.
Project Smoker, '87 603 powered wagon
Hauler, 96 CTD can you say torque?
Toy 73 Cougar xr7 convertible
Acme Automotive Inc.