In my experience it depends on what level of tune has been carried out by SFS. For example I have owned a couple of SFS Banshee rifles-for those that don't know this was the top tune from SFS on a Weihrauch HW95 . The results were very impressive and I would say they were every bit as good as a Venom Lazaglide /(V Mach V glide). Maybe I was lucky. In any event, stage 1 tuning kits give the shooter the bulk of the benefits associated with a full Laza/V Glide at a considerable reduction in the overall cost. Spending more money puts you slap bang in the middle of the argument over diminishing returns.
'It may be that your sole purpose in life is to serve as a warning to others'.