I have the 3.92 rear end with the 5.7L and I like so far. My father has an '02 with 4.7L I think he just has the 3.55 rear end, and my brother has an '04 5.7L, but I'm not sure if his a 3.55 or 3.92... My brother also has a K&N CAI and dual flowmaster exhaust system... My uncle has an '06 and says he gets better than my brother, which could be due to the MDS obviously. I average 14.5L/100KM mostly highway.. and can't get any better than that... but city/hwy combined I sit around 16-17L/100KM, which really depends on how heavy my foot is during that tank. Now take into respect, I am getting my numbers from the OHC... My dads '02 has nothing done to it, straight stock.. and I think he averages about 16.5L/100KM so, you tell me where its at??