I once had Bilstein Tourings front and rear. The rears worked well for 5 years and 75,000 miles except of course for that traditional rattle that started after one year. The fronts retained good compression and rebound for 3 years and 50,000 miles At that point they suddenly became frozen in position during a 600 mile trip. After going over a pot hole on the way home the front shocks suddenly freed up but lost most if not all compression while still retaining the rebound. I replaced the fronts with a set of Boge automatics. Believe it or not the shocks road manners were identical to the damaged Bilsteins. 9 years and 80,000 later they are still in OK shape.
I replaced the rear Tourings with Sach Gas(Mexico). They worked great for 6 months but lost most of their rebound. Next came Monroe gas shocks for a 940. I had to bore out the sleeves for the 240 bolts to work. After a couple of years they started to leak but worked OK without air. A set of IPD heavy duty springs helped with the lack of compression and height issues, but the real culprit of course was the rear trailing bushings. Last year a set of Superpro Poly's took care of slop in the rear. I then replaced the rear gas shocks with an old set of KYB Gas A Justs. OH! I forgot to mention they were the first attempt at replacing the rear tourings. The ride was so uncontrollable and unsafe I yanked them out after only one week. With the new bushing and springs, they do work, but have practically no compression and weak rebound. I would be looking for replacements if not for the developing rod knock and my Carpel Tunnel.
Oh yes... Is it still possible to purchase a set of 4 German made Sach gas struts for a 940...