I'm skeptical of the residual pressure theory. If anything, it may be a symptom of leaky injectors causing flooding after some time sitting.

Skepticism aside, you can test this residual pressure theory fairly easily by turning your key to KP-II several times, engaging the one-second fuel pump burst, to restore the working pressure before cranking. If this fixes things, then consider the FPR or the check valve as the culprit.

Or, if flooded, you can try standing on the accelerator pedal before cranking, to see if opening the throttle wide lessens the crank time for a flooded engine. If this helps, pull the plugs before starting, to sniff out the leaky injector, air it out, then see if it starts immediately.

Finally, if you think you need the cold start valve to assist you in March in Dallas, try disconnecting the valve in one of the cars you're happy with to see if the cold start valve (5th injector) is seriously needed in the morning.
--
Art Benstein near Baltimore

Raising teenagers is like nailing Jell-O to a tree.