It all depends on where the vanes are when you unplug it. Read up on how it functions and you will understand how it can be a poor idea or a very bad idea. I can't really think of a time it would be good. Anyway....if you disconnect it when the vanes are letting a majority of the exhaust bypass the turbine, then you will get your normal boost when the engine is revving high, but you won't have squat for power down low. If you disconnect it when most of the exhaust is flowing through the turbine, you will get great boost down low, but you will get an overboost condition up high. There is potentially a sweet spot somewhere in the middle which might give you some power down low, while not overboosting you up top, but why sit and play with it over and over? It's designed as variable for a reason....to give you the best boost possible at any given throttle/RPM/load situation. Are there better turbos which are not VGT? Sure, but they're typically installed when someone has a lot of work done to the engine and need more boost/flow than the stock turbo can handle. Also, your turbo is not shutting on and off. It is sweeping the vanes back and forth, kind of like a windshield wiper, in an effort to clear off the soot and prevent the vanes from getting stuck. A normal preventive maintenance built into the programming. A feature which can, and has been in some cases, be removed with a custom tune if it really bothers you that much. You will get rid of the up and down whine at idle while retaining the benefits of the VGT.
2004 Excursion 6.0
New HPOP/HPO system o-rings; Updated standpipes and dummy plugs
EGR delete; Rebuilt oil cooler; CCV collection mod
VR Black Diamond head gaskets and ARP studs
Oil and coolant bypass filters; Shell EC-1 coolant
Rebuilt turbo; 250 amp alt; 6000 watts of brain scrambling
One giant 240 pound English Mastiff riding shotgun!