First off, Congrats Timecode on the GN and welcome to the best Turbo Buick site on the net.
You have come to the right place. I must warn you ahead of time, these cars are very finicky and will definitely test your patience. Not to mention SUPER addictive once it's running right. Just read as much as you can on here, and never be afraid of posting up any questions. We were all new at one point and are here to help you get your new fun car squared away. Also, where are you located? You might just have someone local that knows their stuff with these cars and is on here.
Just at a quick glance, it looks like someone was taking care of issues and getting ready to start some hot rodding, but with it sitting for awhile, you definitely need to go over it with a fine tooth comb.
One thing I just noticed, your radiator overflow bottle looks to have orange'ish red coolant. Hopefully.... it's not Dexcool poured into a standard green radiator system. Check your radiator for signs of fluid gelling up as the two coolants are not compatible. If you do see signs of gelling, a complete system flush is in order and you might need to replace the radiator if it can't be completely flushed.
And absolutely stay off the loud pedal until you get at least two tanks of known good 93 octane run though it. You might want to run a bottle of Chevron Techron fuel system cleaner through one of those tanks. And you must get the boost turned down. As has been stated earlier, adjust the wastegate rod out, so that it is longer. When you disconnect it, you will see how the wastegate flapper valve works. You want to adjust the rod so that there is just enough pretension to keep the swing valve snug up against the turbo. Also, you can remove the home made bleeder valve knob that is behind the turbo next to the upper plenum and simply run vacuum hose from the turbo down to the wastegate actuator after you re-adjust the actuator. Remember, the longer the wastegate rod, the lower the boost, the shorter the rod, the higher the boost. You probably have the equivalent of 85-87 octane in the tank if it's been sitting for a while.
Here's the links to the "Spring Cleaning" as was mentioned earlier, and one of the sticky posts.
http://www.gnttype.org/maint/basics.html
https://turbobuick.com/threads/info-for-new-turbo-regal-owners.380856/
On your Scanmaster, if you have it mounted on top of the radio pod, I highly recommend that you relocate it to the top of the dash, so that you can see it while driving. The first screen that pops up after it initializes is the O2 milivolts and degrees of knock. This is your number one screen that you need to watch whenever you start tuning/running the car/making wide open throttle blasts or WOT.
Here is a quick video that will help, along with a little bit more involved tuning step by step.
But you need to give it a thorough Spring Cleaning before you start tuning and cranking up the power. The TE44 on it now, will support enough power to get into the low 11's.
Keep the boost turned down, down, down with 91-93 pump gas. Typically in the 14-16psi range. But once everything is squared away and running good, you can turn it up to 17-18psi with good 93 octane.
The thumbnail image on this video is dead, but the video does work.
These next two links are older, and info was published by one of our OG board members
but it absolutely applies with today's tech.
http://www.vortexbuicks-etc.com/Scantool_Readings.htm
http://vortexbuicks-etc.com/TuningBasics.htm
There are tons of other very helpful videos on youtube as well as the treasure trove of info on this site.
One more tid bit, you might actually have a Maximum Effort chip as the dial style wheel was what was used on my Max Effort chip circa "99-"00. I just sold a Caspers Ultrachip that was in my GN when I got it and the dial had two push buttons to move the selector. Pulling the ECM from the kick panel, removing the cover and popping the chip that the grey harness is connected to will reveal the label with the info we need to ID it. Disconnect the orange single ECM power wire located behind the battery and use care when rocking the chip length wise to remove it from the ECM. You will see the sandwiched secondary chip that the grey harness connects to on top of the main chip.
Take a well lit, close up pic of the fuel injectors, and the back of the turbo and that boost control valve, and we can help narrow down what you have and what we recommend to help keep you from blowing a head gasket or worse. Heck, anytime you have questions or concerns, snap a pic and post it up. Detailed pictures help us immensely when diagnosing or figuring stuff out.
And one last big piece of advice.
When you change the oil and filter, and I hope you do this asap, make sure you order a bottle of ZDDPlus additive from Kirban. One bottle will give your oil enough zinc / phosphorus ppm that the stock style hydraulic flat tappet cam and lifters need to survive. This is crucial and I would not drive it another mile before doing this. You have no idea if any additives or ZDDPlus were added in the current oil and there's no sense in you wiping a cam lobe or lifter because lack of protection.
http://www.kirbanperformance.com/product/445/ZDDPLUS+4-OUNCE+BOTTLE+(1)+#7176.html
Congrats on the new to you GN, welcome aboard and hope some of this helps.
-Patrick-