Hello Heidi...per my PM I have isolated a rattling noise at 2200-2300 RPM...I posted some vides of the noise. I went through many steps to diagnose, including belt tensioner inspect, getting the correct belt on to center the tensioner in operation, cerefully reviewing shifter/brackets/lines/exhausts etc looking for the noise.
http://www.turbobuick.com/forums/threads/rattle-noise-at-2200-2300-rpm-in-drive.411009/#post-3398373
I finally realized it was coming from my transmission. I did this as one day I mistakenly left the garage with the TV cable unhooked and the noise was gone. With the TV cable hooked back up the noise returned. I can move the TV cable adjstment and make the noise extremely loud (with the cable adjusted further from throttle) or very quiet with the TV cable adjusted toward the throttle.
There are many sources for ratttles that vary with engine speed, for me this one has alluded me for two years and two Hot Rod Power tours. I do not have the funds right now to go through the trans so I am just enjoying the car as much as I can until I can fund the trans work.