[AT] GM Flex Fuel vehicles

[charlie hill]

I have a question for the resident GM experts.

I have a 2006 GMC sierra pickup.  That same truck and same engine are 
available in a Flex Fuel (E85) version.   I have no plan on trying to switch 
mine but I'm curious about the mechanical differences in the two engines. 
Obviously the computers are set up different but does anyone know what else 
is different about them?

Seems to me that since GM makes them both ways it should be possible to 
change the gas setup to flex fuel with off the shelf parts.
It would probably cost too much and right now it wouldn't make much sense to 
do it anyway.  I'm just curious about the process.

Charlie