So I bought a newer 2003 dak and there seems to be quite a difference. First the 2003 seems lazier than the 1999. Both have the exact same 3.9 with auto trans. the 03 is a quad cab and the 99 is ext cab. The 2003 gets about 1.5mpg better fuel mileage but feels way under powered compared to the 1999. Did they change anything in the ECU? even the cruise control is way different. The 99 would hold her speed to within 2mph by down shifting sooner while the 03 losses 8-10mph before down shifting out of OD. I can see having the quad cab feeling less powered than the ext cab but why the better fuel mileage and different shift timing in the tranny? Even after moving all my mods off the 99 to the 03 it still feels like a 4 cyl compared to my now back to stock 99.

These are the mods I did. 20% under drive pulley, swap clutch fan with a 18" electric fan, ported throttle body, Autolite 3923, and Flashpack tuner set for performance.