Actual MPG figures?

All efi motors burn more gas when its cold out, you cant do anything about it.
Colder temps = more feul added to the mixture to keep the motor from running lean, you should have a tiny bit more power tho.
My car burns more gas in the winter too.

Good to know it's not just me...

So far I found about a 5 mpg drop from the cold weather. I thought maybe it was me playing with the fuel programmer, but this indicates that the stock ECU map does richen things up for the cold. It also means I will probably need to adjust the program when the temperatures get warmer.

All of us can go without programmer by only adjusting resistance of temperature sensor circuit in a proper way. There are so many e-bay listings for such kind of "power tuners"...
The other question is range that our ECU would accept without switching into default "safe" map. That is why Power Programmer is still popular for DIY tuning.

Quote :

It also means I will probably need to adjust the program when the temperatures get warmer.

I don't think so.. If you found digit combination that is good for you, no need to change it then weather changes.