The main advantage of fitting the EGR blocking plate is to stop soot from the exhaust clogging up your inlet manifold. It redirects it all back out through the exhaust, where it was supposed to go. This also results in cleaner engine oil, which in turn prolongs the life of the engine and gives better fuel economy. It also causes the turbo to spool up faster and sooner.
For more information, please read the following documents
Items 1-12 of 52