The addition of a tuning kit from the like of V-Mac or Maccari will transform the rifle. I have a HW 35 and an 80 that have been 'Venom' tuned, and they are excellent. Wiehrauch make a quality rifle, but the tuning components are hand finished and thus in a springer make a noticeable improvement.
The main areas are consistancy, you will find shot on shot (after bedding in) that it will be ultra cosistant. This assists the accuracy. There will also be reduced recoil and vibration, which again not only improves the 'feel' but assists with accuracy. The 'lock time' also will be different, which gives an impression that the rifle shoots a bit 'snappier'.
Both of my rifles were stock, and then sent to Venom for the conversion. V-Mech is basically one of the original 'Venom' team and he operates on his own now. I wish I could help on where to obtain a V-Mech kit in Canada. Mine were converted when I lived in the UK. You could try contacting them direct?
You will never recognise the rifle post 'tune', a real upgrade.
Candocad.