Koni pre-loaded dampers made a massive improvement to my 2001 p38. With the old OEM units, I felt every line and joint in the road and the tram lining was quite noticeable. Konis made it very useable. I haven't changed steering damper.
The gas in shocks is to stop the oil boiling and forming bubbles nothing else. Your old units where obviously knackered. OEM shocks are as good as anything.