The Tx and the Rx have absolutely nothing to do with the carb. At least if you have your throttle trim turned all the way down like you should, then it won't, no, wait, it still won't have anything to do with the carb even if you have your throttle trim up. You guys do know that you don't want your servos to control your idle, it should be up to the carb alone to handle that. You need to have your throttle trim all the way to zero, then set your idle screw to where ever you want it.