i test drove two trucks,
a 2005 8.1L sierra 2500HD SLE allison,
a 2006 8.1L sierra 2500HD SLT with 6-speed allison.

the 2005 had a lot of pep, step on the gas pulling out of the lot and the truck moved. I was impressed. the 2006 which had lower miles and is the truck i want was much slower accelerating. so much so I am posting here looking for answers why before i buy.
Could the 2005 have had the torque management tuned out, is that the likely reason? Or does the 2005 model year maybe not have torque management on it that the 2006 does?
thanks, any help asap appreciated.