your shift kit (i'm more familiar with bigger engines)will give you smoother shifts when you are driving at a normal rate, when you are pulling away in first gear at w.o.t.the shift kit will shift for you, (leave it in first)when you reach the red line it will shift hard automatically.
believe it or not it's just a plate with a few balls for the fluidways, that's why they are cheap, the cheapest will still work well.
unless you run at w.o.t. from the hole, you don't need it.