Howdy, when you say EGR system are you talking about the PAIR valve (air injection from the airbox into the exhaust port) or some sort of EVAP (charcoal cannister for fuel tank venting) system or something else?
Sorry I no longer have a CBR to look at but I know my 2020 SV has the crankcase breather venting into the airbox. When we tuned it on the dyno we did some runs trying different set ups where the breather was a) blocked off and then b) left open to vent into free air. Turned out the best set up, by slim margins admittedly was the stock set up with the crankcase venting into the airbox.
Those technical folks and engineers employed by Honda are pretty good at their jobs. They've been dealing with moving targets mandated by global emission standards for decades now. They've become pretty good at fine tuning their bikes to address performance, above-average-for-class fuel mileage, and cleaner burning engines.
Hard to believe, but sometimes it's best to leave the bike as is from the factory.