The std springs do have very heavy tension.
However, you can reduce the tension by stretching the original spring a bit. Remove the spring and place one of the bent up coils in the vice, Then with a pair of gips, moles, pliers ets, pull the other end bent up coil. Don't go mad but pull it enough so that the overall spring length is stretched by a couple of mm and then try it.
It does make a difference but do it carefully or you may find that there is not enough tension to close the throttle valves? If that happens you would need to cut off the existing bent up coil and bend another one up.