There are three vacuum lines in the system.
1. From the head to the boost control solenoid - don't touch
2. From the boost control solenoid to the wastegate - pull me
3. From the throttle blade to the wastegate - don't touch
Pull number 2. Its easiest to pull it off of the boost control solenoid, instead of pulling from the wastegate. Pull it off the solenoid and leave it hanging.
The factory injectors can support around 13-14psi before flatlining. The only detrement is that it runs slightly leaner (no risk to the engine, not that lean, maybe 0.4 A/F leaner), which can degrade the life of the catalytic converter in theory, although I have never heard of anyone having any code that was caused by this mod and I know several owners will it this way.
Unless you have a pulley smaller than 82mm, you should be perfectly fine. Realize, though, that the ECM only pulls boost above 5800 rpms (slightly sooner in first), and that's the only area in the rpm range that will be affected. I can tell by watching my boost gauge when the ECM controls the boost. Its rpm based, not pressure based, probably so you don't slam the rev limiter at full boost, till you reach around 15 or 16 psi, at which it will cut in no matter what the rpm is. If you track or drag race the car, you will notice the gains. During normal driving under 5800, the factory boost control is not active, and the car will feel the same regardless of whether or not you have the line undone. If you simply pull the connector off the solenoid, like I did at first, it sets a code on key up, so don't do that. I would highly, highly recommend the shift lights on the steering column, so you can better take advantage of the higher rpm power without tanking the reve limit.
All of this is assuming you are running premium full, which, if you're not, you should be drug out into the street and beaten
If you run 87oct, the ECM will pull spark and you will drop to around 180 hp on a warm day.
Final note, be sure to correct the wiring on the aftercooler pump, if you haven't already (corrected in the factory if you're car was made after 1/1/05 according to the service bullitin). It takes 5 minutes and is a huge help with modified cars.