Hi all i am new here and reside in Ireland. I had a 99 p38 diesel for 8 years and never really let me down. Had to sell her as she was growing tired as a daily drive so sold her to a guy for classic shows. However the bug has bit so i have purchased another replica which comes with some issues. She is better than mine overall but the engine was change by the previous guy and firstly the glowplugs only heat with direst current so need that sorted. Main issue is she will start but will only run if revved and then dies. I will check timing and all sensors but would like some ideas from the treasure trove of P38 genius that resides within

Welcome here. Welcome back to the P38. There are some guys here with diesel experience (not me) who will no doubt chime in in due time.

Welcome. I also know very little about the diesel, but there are others who will no doubt pop up once they are sober.....

Hi, welcome to the site. I have got a relatively clear head at the minute. Family members always buy me whisky.
Glow plugs are cheap and easy to replace Glow Plugs
but a new relay is quite expensive Glow plug relay
You can take the existing glow plugs out and connect to a battery to test them individually, but as they are so cheap, I would just change them all.
Engine cutting out could be one of several issues. Do the easy tests first. Unplug the MAF and run it without it connected. It will revert to default settings. Assuming yours is a later model with a plastic inlet manifold.
Next check the intank pump. Method is in Rave. Run some diesel into a jug. 180mls in (I think) in 12 seconds, but check.
Have a good look at the diesel. Check it is clean and no water.
Is it chipped or have an add on powerbox?