the way i tested mine was

lift back seat turn on ignition listen for noise you may need to try start it to get the pump to make a noise

next get in the back and check if its getting power with a multimeter

and lastly i took the engine cover off and theres a small valve like a tyre valve on the fuel rail stick a pin in the valve and check for pressure (it should be strong) if it dribbles out the pump is gone {not sure if m44 is in the same location}

you symptoms are slightly similar to mine but the reason i didn't post earlier is because i couldn't get the car to run but you can so maybe your is just about to fail

when was the last time you changed the fuel filter

id start by trying what i siad above anyways at least you can eliminate then