Got my LS-1 swap running last month and just sorted it out enough to start putting miles on her. I have new tensioner and idler pulleys on and a brand new Alternator and waterpump also. I even replaced the damper when the pulley walked off the center hub so everything is new.
Why the post?? I had a squeal that wouldnt go away and drove me nuts! Come to find out I had routed the PCV tube from the passenger valve cover to a port behind the throttle body. It pulled so much vacumme that the rings were....well ringing! Moved it to the port off the front of the TB (air cleaner side of the butterfly) and Viola! Fixed.... quiet as a church mouse now.