Does the m21 run as a IDI or DI system?

[///ARINUTS...]

IDI - Indirect Injection diesel engines: the fuel is injected into a pre-chamber or swirl-chamber before going on to the combustion chamber.

If the 524td is an IDI is it a pre-chamber or swirl-chamber?

DI - Direct Injection diesel engines: the fuel is injected straight into the combustion chamber.

If the 524td is DI, which kind of DI is it :

Types of DI diesels:

TDI - Turbo Direct Injection
CDI or CRD - Common-rail Direct Injection
PDI or PD - Pumpe Düse Unit Injection (Direct Injection, each injector has its own pump)

[altus22]

I'm 99% sure it is indirect injection.

[dieselguy]

The fuel is injected into a pre-chamber. The glowplugs are located in this chambers. The fuel hits right on the plugs and it will ignite directly. (Coldstart) You will normally reach higher revs with an indirected injected dieselengine vs direct injection.
I rev my 524td (manual trans)to 5200rpm, and the engine like it!