The most common things to make a Chevy 3100 V6 to lose power at the 50 to 55 mph range is a clogged fuel filter or incorrect ignition timing. A lack of fuel will starve the engine, while incorrect timing will make them engine stumble.
Its has HydraBoost Braked, operates off the power steering pump.
power steering pump or pully may be bad causeing more stress on the belt witch strains the motor an makes it lose power
a vac leak
catalytic conveter maybe
alternator could have gone out running the battery dead.
You Probley have a blowed head gasket.
The alternator would be your best bet. Go get it tested.
engine misfire. i have a '96 Chevy blazer but i don't have that problem, i was reading reviews on the car and found out that some of them do that.
Could be a plugged fuel filter or a plugged catalytic converter.
Range rovers were built for sloppy driving they don't allow you to gas it like a GMC,Chevy, Ford
wire on the starter has a fusable link check that and wires that run to the box
Try lose there power by