As a long time experienced gas engine user (whole ZG range, several 3W engines up to 156cc, BFM engine) I have dealt also with this spring issue. Lóóóng time ago I removed them completely. That proved a bad idea, the spring also holds the throttle valve sideways against the inside of the carb. Removed the valve can vibrate left and right on its axle against both sides and on the long run this wears the valve to the point that it leaks air, You cannot cut the engine any more by closing the throttle.
Later (weak servos and batteries) I just hooked them out, trying to save on bat power.
But for long time now I leave them as is. As already stated before, it takes all play out of the loop, RPM control is more precise. The little extra juice that it costs is just negligible nowadays with good servos and Lipo power.

BTW as a sidestep I did loose throttle control due to servo wear on a 130cc engine. It must have been 4-5 Years in place, which means a few THOUSAND aerotows in my case. Shear luck for me that it happened right after landing. But since 10 Years I use on all my gassers with electric ignition, RC controlled switches, so when I cut the engine (the e-switch runs parallel to the throttle), the e-switch cuts it too. Double safety. In my opinion the ones from Stefan Merz (SM Modellbau: http://www.sm-modellbau.de/shop/inde...fa1e33f3874340 are the best. Light, small, simple to operate.
Forget about the mechanical switches in Yr ignition system, prone to generate trouble and if trouble develops in flight, You cannot control it.
The e-switch, when the equipment is turned off, cuts power too, so You don't loose another Lipo due to low voltage damage because You forgot to switch it off. The engine cannot start (curious kids turn props...) if equipment is not on.

Indeed the only mod I make nowadays is removing the idle stop screw.