Piaggio Porter 1.4 diesel 2001

Hi all first time to the forum as I have search hi and low to try and solve this issue but have come to no avail

My piaggio Porter 1.4 diesel has quite a interesting fault and it has been to 5 garage and none have managed to diagnose this fault .

When I start the engine my van will run for roughly 15minutes after the 15 minutes a small shudder on the engine after another 5 minutes the shudder gets harder and the engine starts to choke out and lose power if I leave it longer enough the shudder becomes so harsh the engine loses all power and stalls and won’t start up after.

I have replace numerous parts:
Fuel pump
Fuel lift pump
Fuel filter
Alternator
Starter motor
Air intake

There are no faults on the dash and no fault codes stored in the ecu

I have check the fuel cap and drove without one on to see if there was a vacuum issue but I just cannot get my head around how it runs perfect for 15 minutes with no issues then suddenly dies which makes me think it’s not a fuel issue like a injector or a glow as it starts up but more along the lines of compression or fuel mixture

If anyone could shine some light on this would be awesome