I found online a kit to block off all three, is there any benefit? or what is it for? I drive a 1995 honda accord ex 2.2 vtec.

 

On a street car, no.
Deletion of said components, not for power but for simplification by reduction of components on an offroad vehicle.
Installing those block off plates on a street car would require retuning of the ECU to be properly done on a dyno, and in the end would net you F all in power gains.

 

Removing the EGR would require a retune. I never had a boost valve, I removed my FITV because you simply don't need it (the IACV can easily handle the load), and the EGR when removed keeps the manifold cleaner, cooler, and more simple to service. But, like I said previously, will need a retune.

 

^everything said above by those 2 essentially. i've been running a block off plate instead of the egr, its soul purpose was to cool the intake side of the combustion chamber when cruising(to help prevent the air/fuel mixture from pre-igniting caused by the extreme combustion chamber temps aka engine knock/ping). without it your air/fuel mixture wont be disturbed by the relativly hotter recirculated exhaust, thus in the right cenario, will result in a slight power gain. but when i deleted mine, it caused my engine to have alittle hesitation during acceleration between 3-4500rpm but pulled nice and strong up top. a good tune brings out the best of what this modification can do.

 

You coulkd also run a higher octane to help aid in getting rid of the predetonation

 

Common misconception.
The recirculated gases do not cool down the combustion temps. The mixture is diluted with the spent inert gases, this diluted mixture will not create the same power levels. Since not as much energy is created, not as much heat and pressure is created during combustion which reduces the creation of NOx emssions in the primary combustion sequence. However, since EGR is only activated during part throttle operation full power is not required. At WOT EGR is not activated, thus does not affect power output usage.
There is no scenario. Simply deleting the mechanical side of the EGR system is going to cause loss of economy, and cause preignition issues. Timing is advanced during EGR operation to complete combustion.
That hesitation is due to incorrect removal of the EGR system. On a street car it is pointless to remove EGR, the work and money spent to properly delete it will not net one with any meaningful gains.
Correct deletion of the EGR system will only net simplification of the onboard systems. Nothing more nothing less on an otherwise stock to mild street car.
Pointless. Even if the higher octane reduces audible detonation the timing and fuel tables are still incorrect.