Those listed vin's were for more so noting those cars with the 'baffled style fuel tank' and though related really the PCM programming was the noted issue.
Your fuel pressure reading of 60 is within range (low of 50 something, cap of 62).
What got me going toward less than optimal PCM tables is that your issue seems to happen when it thinks it's warm but not cold (in a nutshell).
At least your mpg is a lot closer to normal now.
If you don't have a reference and need some info, PM me, I have the GM software for '05 and older on a server in my house. I can at least copy/paste for ya.![]()