I'd have to disagree with you about the soot in the intake. As an m/b tech I work on a lot of different cars. The gasoline cars have the same problem. The M104 tends to clog it's EGR port but only within a few inches of the intake, shortly after where crankcase fumes are mixed with incoming air. The pipe is over two feet long and only 10mm od. However it only clogs up right where it goes to the intake. Same thing as with the diesels, the crankcase vapor gets very hot near the EGR port and evaporates the lighter components leaving the crud to block the port. Not nearly the soot as in diesels but the exact same phenomenon happening.
Even without EGR on a turbo diesel the heat from the turbo would evaporate the lighter components of the re-cycled crankcase vapors and still crud up the intake. Granted the soot isn't helping the situation but isn't the root cause of the problem.

I'd be willing to bet that the euro 603's have either a different part # injection pump or less total timing (and probably both) With EGR the exhaust gas acts as a buffer during combustion, allowing the mixture to burn slower, which in turn allows you to extract power over more degrees of crankshaft rotation. Without egr the burn is faster which results in a spike of combustion pressure early and no usable energy late in the stroke. The difference between the two burns is like the difference between shoving a door open and running face first into it at top speed. Either way may open it but which way do you want to repeat 3000 times a minute?