what is the overall amount of time this takes place in?
does the temp affect how long this whole process takes?

Something to remember, when you start it, all of the injectors are firing, so you're dumping a lot of gas right at start up, and it can take a few moments for the ECU to get that back under control. Most of us wouldn't even notice it without watching a wideband.

I'm trying to remember, you have a pretty decent list of mods don't you? Been a while since I've been over in the green motoring section.
You've got your wideband set up to still send a signal to the ecu, or do you have that bypassed entirely?

there are a few things that can cause this
ranges from coolant tempt sensor, rusty coolant, dirty MAF, poor ignition timing, weak spark, fuel pressure too high, to something really annoying, like a bad/going bad TPS. My Z would just dump gas when the TPS was going bad. Thing is with that though, it would continue to dump gas even after the ECU pulled the timing back to where it should be, and it would run poorly. Notice it running any differently before or after the AFRs balance out?