[Diesel Nut]

First, from my experiences the stock intake on the Duramax is pretty good, and not really worth changing out until you are going for big power.

As for the tuners, some defuel for shifts and some don't. On a stock transmission, defuel is better for the transmission, but bad for performance. Pick your poison.

 

[Diesel Nut]

So no middle ground here huh?

t.

I guess bad for performance was a little strong. Defueling will slow you down a little, but you will still see more performance than stock. Some guys don't like the way the defueling feels, it can be pretty obvious on some tuners.