I was curious about this post and did some research, you guys can tell me if I'm wrong.

Basically, EGR works by passing a small amount of exhaust gas (4% to 7% are numbers I've seen)into the intake under load conditions that would otherwise result in high combustion temperatures. The exhaust gas lowers the combustion temperature to reduce NOx and also allows the ignition timing to be advanced more than if the EGR valve wasn't operating. The EGR valve is closed at WOT.

So, disabling the valve would potentially increase emissions and cause detonation under certain loads. But, you'd be able to cram some more air and fuel into the cylinder which could make more power if you did what was necessary to eliminate detonation. High octane fuel, reducing the ignition advance or installing a modified cam with more overlap might work? I suppose the exhaust gas being injected into the intake might also mess up the flow of the intake charge but I think Toyota handled that by injecting the gas near the throttle body (on my 3VZE there is a long tube from the EGR valve inside the intake to accomplish this).

So I guess if you know what you're doing, then blocking the EGR (done with other modifications) seems like it could make the engine more efficient. Otherwise it doesn't seem useful unless you need a temporary replacement for this expensive part.