My 08 GMC Sierra has Active Fuel Management, and it does work while using cruise control.
1985
No, none of the SRTs of that era had active MDS.
NO See EFI Live
Active fuel managment was first introduced by Catillac in 1981. Since Catillac was known for their big V8, this car featured a system that would make only have the cylinders fire.
Yes, it really works. Estimated performance on EPA tests show a 5.5%-7.5% improvement in fuel economy.
ADD FUEL
Pull the fuel pump fuse.
You cannot turn it off. Only a custom tune can do that. Custom = Warranty Void
It does not have a fuel cutoff switch, you have to remove the fuel pump relay to disable the fuel pump.
Pull the fuse or fuel pump relay.
Yes. Many engines do not have fuel management systems.