That is a great question Barry. I've tried dozens of E strings and as Pky said, I settled with Pirastro Gold. Lately I tried three E strings by Daddario, the same one that CatMcCall is referring to, a Zyex which is one of the best but I too have noticed the whistling, Helicore and Kaplan. I am also super picky about my E string. The Gold Obligato E string is maybe the best E string I ever tried. I just stopped buying Obligato cause of the price.

If none of your other instruments do it you may want to switch E strings to begin with. Some whistle more than others. Daddario makes a whistle free E string but I am not 100% satisfied with the sound of it.

It is called "Kaplan Solutions Non-Whistling Violin E Strings". It might be well suited to your electric violin too.

Tips to avoid whistling strings:

Make sure no part of your finger is touching the string when playing the open string. Sometimes when we play chords and double-stops with open E strings we accidentally touch the string without even noticing it. Also if you perspire and there happens to be some perspiration left on the string it can whistle. The whistling comes when the string doesn't vibrate quick enough so a little attack or added pressure can help but not always suited to the music. Wipe all the excess rosin off the E string as the buildup can also cause whistling.

We were talking about steel strings earlier and I admit that Helicore strings are exceptional for being steel. Very impressed with my recent test. I didn't like the E but the rest of the steel fiber core Helicore strings are great.