Hey Telstar
I think I have exactly the same issue with my 1999 S40 1.9 T4 Auto. I get a lurching/juddering at about 3500-4000rpm which seems to correct itself when I ease off the throttle a bit. It's deffinately getting worse though as now I have really bad acceleration even in sports mode and have had to drive around in economy mode instead
Please keep the thread updated as I'd love to know if you get it fixed and what the solution is!