Check the FAQ Locator, since Brad Bauer has had the VFAQ for this subject available for some time now. It's also discussed in the DSM Top Ten FAQ.
Many people have installed these devices. It is now commonplace to see EGR blockoff plates sold by private individuals on the DSM Parts Trader and DSMtrader.com. However, they may not work quite the way you think.
Experience has shown that the only true benefit to installing an EGR blockoff plate is that it helps keep the engine intake clean. This is because the EGR recirculates dirty exhaust gases back to the intake. The carbon and other contaminants from the exhaust tend to coat the intake piping.
While it is true that you should theoretically get a performance increase by blocking off the EGR, in practice the change is so slight as to be negligible. Even this advantage is debateable, since some people claim the EGR only functions when the car is not boosting in any case. Also, 1994 California cars and 1995+ models are equipped with additional sensors to check that the EGR is operating correctly. Installing a blockoff plate will probably cause a 'Check Engine' light on these vehicles.
Blocking the EGR should also affect emissions performance - again, in theory. In practice, it has been argued that the EGR valve is so small on our cars as to provide little benefit for emissions.