I don't have the squeak you talk about,
but is it possible that it is the gas tank if you loosened it to put in the new bar. That is the only thing you could have changed when you did the install. I lowered the subframe to install the bar. I did it this way because I borrowed subframe locating pins from a friend. I didn't like the idea of moving the gas tank in my small garage.
Hope this helps.
Andy
