felt springy? Again I am asking, did you remove the needle to adjust it, i.e. stuck a fork behind it and pry'd it off. Sounds like you're only pushing it back to zero with your finger. That won't do anything, except maybe damage the stepper motor its attached to. Sounds like it is offset 20-30 mph. Take the needle off with a fork, turn the key on, and push it back on at 0 mph. This will be close, you'll have to gps check it later. When you do your final check you can push it on (ever so slightly) and check it, if you're off a couple pop it off and adjust. Would prob help having a friend hold the wheel, with cruise control, on an open flat road.
This is where the trans connector is. But you're problem seems to be only in the needle adjustment. Again, don't worry about this part until you can actually drive the car.