There are several threads on this in the diesel performance forum, this one is a good start:
OM603 semi-super pump testing, fitted with Bosch 6.0mm elements
In this thread GSXR had worked with turning up a KKK, but had limited success due to the design of the turbo. Still, it can be done and if you have increased fuel flow to use the additional air, you can add a small amount of power to your stock setup and a noticeable amount of poke off the line.
This thread is 603, and there are many more threads in the Diesel Performance Tuning forum for 617s, but the ALDA and KKK turbo are of the same basic design.
I've personally never had my hands in a 617, but threads here outline how to check and clean the ALDA plumbing from the banjo-bolt to ALDA as a first step, then move on to checking the ALDA for pressure leak and adjusting, and of course a boost gauge to check for proper turbo/wastegate operation would be next.