Idle bars are generally not needed with modern engines. The idea was to stop fuel from dousing the element, and it is generally considered that this was more a problem with engines of older design, pre-Schneurle porting. They are sometimes used in inverted installations to improve idle reliability, but I don't have personal experience to say yea or nay on that one.

One thing I noted in the advice columns of yore, was to make sure you use idle bar plugs where the idle bar is machined into the body of the plug, versus welded-on as those have the potential to come loose and you can imagine the havoc. No idea whose are and whose are not of this construction, I have not used an idle bar plug in a donkey's age.

MJD