How does Displacement On Demand and Active Fuel Management effect programming the PCM: ECM/TCM? I'm going to buy a new Silverado and am wondering if I should get one of the ones they are calling "Classic" Silverados(Legacy) or opt for one of the new types that has DOD and AFM. The newer ones have a faster CPU and more running memory to deal with these new features, but I don't belive you'll be able to install an aftermarket cam in them because of the special cam lobes and complex lifters they use to shut 4 cylinders off.