It works to an extent but you are much better off removing youe EGR valve cleaning it in carb/injector cleaner with an old toothbrust making sure it opens and closes correctly and re- fitting it.
There has been alot of debate about Blanking/blocking the EGR valve on inported mitsies and i belive there is alot of evidance to sugest thet it is not the best option, i have tried both the ball bearing in the pipe and the EGR blanking plate and found no dfferance in performance or smoke with them fitted but after i removed and cleaned it (it was jammed slightly open i think) all has been well.
hth steve.