Landex, I solved it! I dont know for sure what did the trick though. I am commenting in case it helps others in the future.
1.) I had a mod folder in my GP4 directory, which also held all performance files. But the CSM mod pointed to the performance files in GPX folder. I changed it to the mod folder.
2.) I downloaded the performance update for the 1991 mod by Rot Teufel.
Which one of the two fixed it in the end I dont know. But I am sooo happy it works now, I am several seconds slower now
Thank you for all your patience and help Landex.