Engine Performance problem
1999 Land Rover Discovery 2 V8 Automatic

i am getting the following codes 1300 p0306,308,300 and 1319 intermitantly i have changed plugs and wires and cleaned mass air flow sensor. at first problem cleared up when i reached 50 mph now it does not i have found a vacumn line loose from cruise control. when i reset codes p0306 comes up every time the other cylinder missfires come up at random. i have no power and rough idle