I have a 2000 Buick Park Avenue 3800 series 2 Supercharged and when I first got it, there was some audible whine (in a good way) after a while that whine started getting extra high pitched when under boost. Eventually the whine is completely gone. Without a boost gauge i dont know how much boost i am getting if any at all. Any suggestions on what may have caused this or what parts or pieces i should check on? NEED DIAGNOSED PLEASE

You can't tell if you are getting boost? What happens on full throttle, A good burst?

You could always hook up a vacuum/boost gauge between the supercharger and the intake manifold. This would tell you.

Is the supercharger belt still connected and turning?

i do get a pretty good jump in first gear. Also at higher RPMS i hear a grinding noise on occasion hard to hear over engine noise at that rpm tho 3-5000

your coupler probably needs to be replaced you have to pull the snout off and change oil. also, check the oil level. Also, if you are on the brake in drive at a stop on level ground and you slowly accelerate for a short distance and then WOT gun it, do you have a small small portion of that acceleration kinda slow but then instantly you shift in your seat and then you start hearing a suction kind of noise or perhaps just sounds like a Pressurizng noise, then you haul *** and that keeps going until your rpms drop down enough either from upshift or letting off and then its quiet again. Now go sit in reverese and do the same thing. You will prob notice the reverse is gutless kinda and has different noises. thats because its bypassing boost because boost in reverse is.. weird. Its not a time you usually need to haul *** and you can end up all over the place if not careful esp when the torque kicks in and you may have a bump to steering which in reverese will move you a lot more than forward. then go back to forward, and just gentle accelerate keep it under 2k and notice the noises then. report findings. also verify your airbox has a good air filter, your airbox is not restricted at all, its secured down, and your PCM cover if you pop it off has no mouse nest or anything in the air flow path in that part. then make sure the rubber duct is sealed on the TB and your intake. any leaks in the induction path will make a lot more noise than you almost would think it would.
also at idle vverify your bypass plunger is one way and you can physically actuate the arm sometimes they get stuck and get weird. partial bypass or some other situation may cause weird noise because its intended to be one or the other more or less not held between.

also replace your pcv and clean the baffle and check your oil cap gasket for clean and make sure you dont have a bunch of air pushing out oil cap or suction in

pay no attention to the first one i needed that for a DM. the second one explains the baffle under pcv