Mike,

I don't think this has anything to do with the electronic part of your FI
system. First, if your ken-o-meter is showing good results, that means the
electronics are working normally. Second, your symptoms are too extreme to
be caused by a bad sensor or whatever, and the fact that it corrects itself
soon after starting means the FI system isn't faulty.

This is not really related to temperature, either.

I'm wondering if it could be something in your fuel delivery system, a
physical clogging of the fuel lines or some other problem that would limit
fuel pressure/delivery rate during the first 30 seconds or so of operation.

What happens if you start it, then just let it idle for a few minutes? Does
the problem go away?

Another possibility would be something loose in your cat or muffler creating
too much back pressure until, after a time, it moves out of the way because
of vibration  or pressure and allows the exhaust to flow correctly.

In any event, I think this is something physical (not electronic) that
corrects itself due to engine vibration or exhaust pressure or fuel pressure
after the first few minutes of operation. It's not going to be a vacuum
leak, a sensor problem (except possibly a bad connection), or the like, as
these would not disappear so quickly and with such predictability.

Geza