? About progressive rich Stoich

[TheMechanic]

Got a simple (Hopefully) question that I just can't seem to find using the search function. On Gen3 the Stoich it is usually a set approx 14.6xx or somewhere near it all the way across the table and I believe it is other "things" like PE that multiply or divide upon this number to modify the ultimate command.
What confuses me is on the Gen4's it looks to be a downward richer Stoich that on many I've seen go all they way to approx 9.0 give or take a couple of tenths. The other thing I can't seem to find out (on gen3 never needed to because it was all the same number) is what does the % represent? Throttle position? Load? Cylinder airmass? A fuel modifier like percentage ethanol?
So if Gen4 has a Stoich that goes to 9 what modifies it to bring it leaner the most? Obviously nothing is going to run well for a street light mod vehicle and anything below 12.00 even at WOT.
Thank you in advance.
Danny

[5FDP]

The sliding stoich from 14 to 9 is for alcohol content.

The more alcohol, the lower the stoich. The PE table will still work off the 14.68/1.XX to read the commanded AFR even if you are using E60 fuel.

[TheMechanic]

As always thank you for your knowledge on the subject. I've learned a great deal over the years from you posts.