Land Rover Repair: 1997 Land Rover Discovery LSE Engine Dies, land rover discovery, crank sensor

Question
I am a mechanic who hasn't had a lot of experiance with Land Rovers.  I have been working on a 1997 Land Rover Discovery LSE.  As it is driving it will suddenly sound like it is starving for fuel and then die.  When I first got it there was two codes on the computer, P0420 and P1172.  Before I got the vehicle it had sat at a different shop and I beleve they replaced the fuel control module.  I have replaced the fuel filter (completely plugged) and the spark plugs but it still had the same plroblem.  I heard a bubbling noise from the fuel pump and replaced it eliminating that problem.  I dont have any codes on the computer but still have the same problem.  Any suggestions

Answer
I would start by driving the car with a fuel pressure gauge attached and check the pressure when the problem occurs.  If the fuel pressure is OK, I would try replacing the crank sensor.  If the fuel pressure is low, I would start with replacing the main fuel injection relay.