Here's what I would do as a guy who's bought a few Buick's sight unseen and been around them a good while.
Get the car home. Find the Boost controller and turn the boost down as far as it will go. I believe counter clockwise on the knob. Pull the oil out of the car and examine the heck out of it. Replace it with good oil (I use VR1 Valvoline 20/50) and make sure to put a Napa Gold or Wix Filter on it. The part numbers can be found here.
Next, When the car is running again, go through the scanmaster and check all the readings including any possible engine codes. You can search here for a list of what the scanmaster should typically show on a good running car.
Ok, all that looks good, Pull the lower kick panel on the passenger side and remove the ECM. There is a little screw that takes the plate off that hides the chip. Remove it and figure out what you have. If it's not a Turbo Tweak than replace it with a Turbo Tweek that's set up for this car.
After it's back in. Change the plugs. There are a few things people like here so find out what you want to go with. Guys use Autolite, AC Delco or NGK. Again, the part numbers can be found while searching here. I use NGK UR5 right now. Sometimes I try others for the heck of it. I've not had good experiences with the Autolites in these cars for some reason. Only Delco and NGK.
Go around the whole motor and check every vacuum line. Zip tie the connections as they like to blow off. Make sure there are no rooted vacuum lines.
After you feel like the car is pretty stable and no alarming matters you are good to start making wide open throttle pulls. Make sure there is fresh 93 octane gas in there. At this point I would research how to tune with the scan master so you can start increasing boost and get back to 18-20 psi safely.
These are just some ideas about what I think your original question was.