that's just creative sales banter to make you belive you are getting something you as a driver/owner need to have to save you money. now they use egr coolers to get the gas temp as close to ambient as possible. also inject pig p**s into exhaust. all to save the environment so we can all hug a tree if we want to or not.
blanking egr on the z22se and similar engines is cheaper than fitting a new valve and means no more future valve failure.
I blanked mine on the Vectra and corsa, z22se and x20xev, had dyno runs before and after on corsa with no power gain, no saving on mpg, slightly higher co2 at idle and high idle but lower hc at high idle. that was in my experimenting days after I got told its impossible to get the x20xev over 180bhp n/a. up to 226bhp n/a now.
and still passes mot emissions, blanked egr, oil catch tank, removed sai, still using a cat though.