I have a 05 trailblazer with the inline 6. My parents have a 02 which gets a lot better mpg than mine. Mine has the 3.42 rear end and theirs has the 3.73 rear end. I figured that the 3.42 would be better for mpg but has turned out different. The problem I have noticed is that it wants to drop out of OD all the time, even with a light head wind and rolling down the interstate. I was looking in the tune file and noticed that a guy can change settings on the tranny but what ideas do you guys have to help out the mpgs and hold od? Is it even worth burning one of my vin tags on?