Did you just get this car? If so and you havent done any maintenance then definately do so (as already suggested). This aint nothing special, just what you should do with any used car you just bought, so you can at least know where everything stands. Do plugs (AC Delco CR43TS gapped at .035 will get you going). Check your wires also. If they need replacing, either go with some new Delcos or with a type sold by a reputable TR parts dealer. These cars are rough on just any plug wires. Change/get a good fuel filter (important). Check your PCV valve. Make sure your air filter is in good shape. Change your oil (use good oil, remember this has to do with the life of your turbo too).
After the maintenance stuff your next step should be making sure the car is breathing. The point about the shape of your catalytic convertor mentioned above, is a good one. Make sure your exhaust doesnt have any restrictions (i.e. the cat). You will definately want to upgrade your stock exhaust sometime to something more free flowing but for now thats not the issue. You need to just identify your problem(s) and get the car performing like stock should (high 15's @ high 80 mph (88), instead of 19 sec @ 70). Again, this doesnt have anything to do with your current problem, but you will also want to upgrade your air intake setup in the future. Get a K&N cone and get rid of the stock air filter assembly.
You definately need some way to read what your car is doing. Get a boost gauge and a fuel pressure gauge. It would also be good to have a oil pressure and water temp gauge. You need some way to know if your getting detonation/knock retard. A scantool is a must. If you dont want to shell out for a laptop and Tlink or Directscan, then get a Scanmaster (which actually is easier to deal with on an every day basis than the laptop). At the least get a knock gauge of some sort. The simplest would be Casper's audible knock gauge which lets out a LOUD obnoxious beep to let you know you need to back off the pedal.
The #1 issue you need to worry about is the condition of your fuel system, which should be the FIRST upgrade you make (get a Walbro 340 w/ hotwire kit, and adjustable fuel pressure regulator; as you continue to mod, you will want to upgrade injectors aswell). Again, as long as you are able to monitor fuel pressure (make sure your FP is matching your boost pound for pound) and knock (via scantool or knock detector) this is not something you should have to do to run the good stock times, but something you definately need to do for the future.
Detonation is what your first concern will/should be. The catalytic convertor is something to check. The other thing I can think of is your tranny (how is it shifting?). Burn outs and how you left from the line isnt going to be the cause of why your car is 3+ whole seconds slower than stock.
Good luck.