(quote)I generally remove the throttle spring. However, if you want to keep it, remove it and cut off a couple of truns which should weaken it somewhat.

(my reply)
Shorten a spring, any spring, and it gets stiffer/stronger. In other words, the spring rate goes up. Imagine a torsion bar(which is just a straight spring); at say 1 foot long it takes 100ft/pounds to twist it 90degrees, shorten it by half and 100ft/lbs will barely turn it.