Perhaps after shooting the S400, the 2002 just does not reach the mark any more.
I think this hits the mark. No pun intended.
You need to pick an action, a stock, a scope and finally some pellets and just stick with it for longer than one Wednesday.
All this swapping around like swingers at a Rock reunion is doing your shooting no favours and it will only get worse once the dribbling sets in...
Just get the custom stock, stick the Steyr in it, plant a 20-50 or your March on top and be done with it, then just shoot the damn thing.