Long crank times when COLD

[Amarillo_Powerstroker]

What causes long or extended crank times when motor is cold...?

Cranking times are perfectly normal when motor is warm and very rarely normal when motor is cold. I know this is not "normal" as this issue just started occurring this year over the past few months. I know that leaking dummy plugs, standpipes, and the all too common STC fitting are all causes of long crank times, but I was under the assumption that a leaking STC fitting only causes long crank times when the motor is warm. So, can the STC fitting be the cause of long crank times when the motor is cold?

The dummy plugs and standpipes are the only other common things I can think of that can cause this issue. I have already replaced the drivers side with the updated dummy plug and standpipe when I was in there for the #8 injector, but I haven't touched the passenger side yet. I also have the updated FPR blue spring to bump up the fuel pressure.

The glow plugs and GPCM seem to be working properly according to the AE software. Truck in sig. has almost 80K miles.