for running empty on the highway. does it keep boost and fuel metered down or what?

A program can increase fuel economy by "optimizing" tuning. This is often impossible in factory tunes due to restrictions on emissions, drivability compromises, etc. Basically, the factory tune has a lot of "criteria" that have to be met that are sometimes not the most fuel efficient, although they strive to make it as fuel efficient as possible within their restrictions. They actually do a pretty good job, because I haven't heard of any aftermarket tunes picking up any huge mileage, but even a few mpg is good with diesel prices over $2.50 a gallon.

Better question...i have a diablo...and for those of you who use it which setting do you see the best unloaded mpg...thanks for any input

Better question...i have a diablo...and for those of you who use it which setting do you see the best unloaded mpg...thanks for any input

I dont personally own one, From what i gather around here, The 85 HP setting would be good. Easy on the tranny though...

advance the timing.. this gets the highest pressures & the best fuel economy.. dump more fuel in for more power..
The factory had to obey fed air quality rules.. so the fimilg is a little later for lower peak pressures, and less nitrogen oxides? the things the cats are cleaning up..
it is a trade off of power, economy, and emitions..
if the epa gets really board, they can enforce the "tampering with a smog control device" part of the laws..

for running empty on the highway. does it keep boost and fuel metered down or what?
pretty simple actually,with low power your tranny will always be shifting up and down with any kind of grade or load ,your revs will increase exponentially........taking in more fuel. with more power it will go up a grade without downshifting, running at its premium torque output ,keeping the revs lower thus consuming less fuel /mile :D