Compression test or leak down test is throwing your money away. Most of the time, these are done incorrectly and the results mean almost nothing. There are easier ways to find a dead cylinder, if that's what you have, and I doubt that's your problem.

As was previously mentioned, your IP is probably fine....they don't fail very often and this does not sound like their failure mode.

If, and only if, you have gone more than 150kmiles on the injectors, I would pull them and bring them to a diesel fuel injection shop and have them checked out. They should charge you about $5 each to test them.

And save your money on the diesel purge...IMHO, another high tech snake oil that might work in some cases but if your injectors are right, totally unnecessary.

And forget the Italian tuneups. It works when everything is perfect with the car but the engine is a bit loaded up by being babied about town. Most of the time there is something wrong
causing your symptom which after repaired, normal driving gets the car back in shape.

All, IMHO, of course.
240Joe