fitting this egr blanking plate does stop that horrid black smoke blow on take off. the only negative answer to fitting just the one plate is [ as Bods said ]
if the silver coloured cooler tube blows a hole in itself you won,t lose any coolant as opposed to fitting just the single only plate.
as for warranty, buy the stainless steel blanking plate which is the same shape as the other gaskets you will spot fitted to the egr areas and the only way to tell if this blanking plate has been fitted is by eye observation, need to remove it to see if it got no hole in the center.
if by chance something should go wrong with your engine, just remove this plate before any work gets done. 10 minute job to remove and replace.
i have the last model D-22 that was made like you have and have this egr blanked off, [ 1 side only ]