13's is a lofty (but possible) goal. You probalby have a 17 second car to start with. Knocking 4 seconds off anything isn't easy, but much easier with a turbo.
#1. It's not a Small Block Chevy, so throw all of those ideas about carbs, cams, headers, intakes, etc. out of your head. Well not completely out, becuase you will do some of that, but there are much more important things. Like boost, knock, tuning and tweaking.
#2. Do your homework. Read anything and everything you can about Turbo Buicks. Start with the website in my signature.
#3. Get your car running perfectly right. Even if it seems OK now, it might be far from where it should be.
#4. Get a boost guage and someway to monitor knock. Learn about the function of the ESC (knock system).
#5. Did I mention to get a boost gauge?
#6. Realize that ECM cars are different than non-ECM cars.
#7. Figure out your rear axle ratio.
#8. Learn about the '81's normally open wastegate.
#9. Once the cars is running perfectly, turn up the boost. More power, doesn't any money.
#10 Use this message board everyday.
Good Luck and Welcome!