With the egr's blanked, the inlet taken off and cleaned out (just below the egr's will be full of crap) and the fuel pump turned up about 1/3 - 1/2 a turn you'll see high 20's maybe even 30 if you've a light right foot.
They are good trucks, tow well (far better than a landy due to IFS) and are very reliable.
Rust is the killer though, check the chassis and wax oil as soon as you get it.
Don't every press the button which has a picture of an engine on it - it's the cold start which closes a valve in the exhaust to make the engine work harder - the valves jam and it's a pita.
Oh if you've get one which has 2 batteries under the bonnet - it's still 12v but you've the cold climate package. There's a ceramic heater (there's a recall for one of the plugs), when you start the car and put the heater on, the revs will jump up - it's normal.
