I have the helix and after installing it in all 4 possible positions, I removed it. I could not tolerate the whistle. It soundsed like I had a squeaky belt all of the time. I like performance mods, but I also have to put clients in my truck on a daily basis and there is just no way I could listen to the whistle or expect them to listen to it either. It did seem like it made a difference but it wasn't worth it to me. I will sell mine to anyone that wants it. PM me.