It's totally ironic, that I was having a thought about making stiffer shifter springs for my car, and I check Z1 and they have this part:
MTech Shifter Spring
I'm not sure about the details, but what my theory is that a stiffer spring will assist in a faster 2-3 shift. I personally shift my car from 2-3 by just pushing pretty much straight forward - and letting the spring push the shifter back to the neutral axis. My thought was if I had a stiffer shifter spring, it would make that motion quicker and more reliable.
If this MTech spring isn't stiffer - then I have no idea.