My GF's '85 OM617 wagon will kill my '87 OM603 sedan off the line and I'm pretty sure my 603 is running about right. However 4 seconds of "turbo lag" is wildly excessive. My car would already be catching the aforementioned good launching '85 TD in 4 seconds.

Removing gunk from my prechambers and replacing my injector nozzles made a huge difference in how quickly boost would build in my 603.