the 1600s are the 52s? After everyone saying 46s or 49s I've done some searching an seems the 52's are going to make it pretty much useless offroad unless a engine swap is in the near future. thanks everyone for the suggestions and for pointing me in the rite directions. Exactly why I joined the forum! On a side note when I brought my 2004.5 duramax home in completely stock form my dad was irate. He was totally anit-diesel pickup. then after about 4 months I had the transmission built to a stage four and custom efi live tuning done with a few other go fast parts, we went to a 1000' drag race. We drove 77 miles there averaging about 27 mpg at 80mph and raced all day and had the fastest truck there, even against a 1970 c10 short bed 2wd injected 502. Now he understands why I bought a diesel, I pull his mud bog truck to events and get 18 mpg towing, and have a low 12 high 11 second 1/4 daily driver that gets 28 mpg empty on the highway at 70. Everything I learned about my truck came from a forum much like this one. Friendly people and lots of knowledge on the internet!