Its all about combination. Parts have to match or something suffers. The stock tq converter and stock turbo are a match.
Power on these cars is boost and timing. Your limited on boost due to octane. The higher the octane you run, the higher the boost you can run, the more power it will make. In simple terms. When your limited to a certain PSI due to octane, the fastest spooling turbo is what will make you the happiest.
Typical first mods.. scanmaster, injectors, adj fuel pressure reg, 160 stat, adjustable WG actuator, fuel pump+hotwire, and a modern chip. That will allow you to tweak what you have. Once you get the boost to 16-17 PSI.. and you start seeing a little knock readings.. then its phase 2.. increase octane through the use of race gas or put on alcohol injection.
Your car with the above will pickup like 100 to the tire and feel like a totally different animal. This is how you get a Buick into the low 12's/11's vs 14-15 second 1/4 miles stock. Fastest stock turbo car is 11.3 on a 130K mile motor.
HTH and keep reading.. you'll learn a lot on this board.