Thanks Mike. I have no plans of messing with the defuel. Initially when I posted on the thread I was only seeing the last 3 pages. Today I got all 10 pages and was able to get answers to the first 3 questions from the earlier pages. I'll give Duramax Tuner a call and see if there will be any complications when using the PPE or other tuner programs on their locked TCM. It's been a year. Maybe they've found a way to hide their tunes but allow for adjustments.