91 excel codes and issue

[catesja]

I have the following codes stored and need more info as to were to start!

11, 12, 13, 14, 15, 21, 22, 23, 25

I no that a few of them are related and throw when another one does. I have found that 13 is because of 12, 25 and 15 are because of 14, 23 is because of 22 and that 11 (O2 sensor) wants the rest fixed first. So it sounds like I need to start with 12 which is the MAF / IAT / BP sensor. But what could be the real cause?
The cat had issues with a cold start hiccup that went away after warming up, but the cold it was outside, the hard it was to start. Then we hit the teens and low 20's and the car wont start at all. In the 30's and low 40's it would start but stall and you had to rev it alot to keep it running until it was warm, at which time it was then fine. So this has to be a temperature issue, but where to truely start.... I have used the hmaservice.com and found some good info, but what are the chances that I will need to replace that spendy sensor?

Thanks
Jeff