As I recall the DFCO limits are 1200 & 1900 rpm for a stock M6. With stock 3.42s, you would generally not exceed the 1900 rpm limit when cruising on the highway (or at least it would be unlikely that GM would design for that given that is far above the speed limit). Now let's put some 4.10s in the car. It's not too hard to be above 1900 rpm on the highway when moving in traffic going 75 mph.

With that premise, does it make sense to consider bumping the DFCO to something like 2200 when switching to 4.10s?

 

I thought it was values above those RPM's that enabled DFCO. If I'm understanding that right, I wouldn't change a thing since you'll be going to higher RPM's.

 

1900 is the enable rpm. With stock gears, it is not enabled at normal highway speeds. With 4.10s it will be enabled much more frequently.