with an internal waste gate you can adjust the "blow off" point with a wrench. if you tighten (shorten) the rod the waste gate will open faster meaning less boost. loosen the rod and the waste gate will stay closed longer, creating more boost. the turbo its self has nothing to do with the boost really. the intake side of the turbo can have a bigger ratio from the exhaust wheel making it spin slower making less boost. normal turbos that have oil type bushings will spin around 120,000 rpm before they come apart, and the only way to change the boost is by a waste gate. the wheels will change how fast the turbo will start creating boost. for example if your motor only turned 5000rpm the turbos might have not been spinning as hard there for making less boost. if you have changed the carb jetting, fuel, timing, anything really to increase the rpm you could pick up more boost. if it was me i would weld the internal waste gate hole shut and run an external waste gate that you can adjust, like for different alt, and different fuels. when i ran volkswagens with turbos on them the motor would make boost quicker when it was cold and the air was thick, but with an external waste gate it would always pop off where ever i set it. but just my .02
The Beav