Exhaust gas recirc is one of the most doubtfully effective emission control methods I can think of. Feeding exhaust gas back through the intake manifold makes about as much sense as pissing in your gas tank.
That having been said - an aftermarket intake is the simplest way around it, but most of those are illegal in many states. A port blocking plate can be made for many systems, that amounts to little more than a strip of metal with bolt holes in it. The EGR vacuum device may have to have any projecting parts diked off if they pass below the plane of the manifold bolt-on surface, which camouflages the fact of it's being rendered inoperative. You gotta hide that stuff from the SMOG GESTAPO...
They will look for all that stuff to be in place, regardless if they understand how it works or not, but they won't tear your intake down over a fifty dollar check fee. (Or whatever it is these days). If it looks like it's there - IT IS!
EGR is based on thinning out your intake fuel/air charge by feeding exhaust gas back into the system under low power operating conditions - when it has little effect and causes a lean-burn condition. Alternatively, it can "CHOKE" the engine, insufficient oxygen is available for the flame front to propagate.
Frankly I think it's a bunch of crap.
The only GOOD pollution control device I agree on is Positive Crankcase Ventilation - which does benefit the engine by getting rid of acid-bearing gasses that can be harmful to engine wear overall.
When you create a lean-burn condition, your valve stems are in danger of burn-through on the exhaust side. If you've ever had a burnt valve - you know how expensive that can be. The other side of it is heavy carbon build up in the upper chamber areas, depending on how the engine is operated.
My thoughts on the whole thing are to build every engine as if it was going racing tomorrow - to make the most horsepower out of every drop of fuel! That is the most efficient way to run any engine, and that is the least wasteful of our limited resources
Get every bit of energy we can, out of every last DROP of it.
To waste any of that fuel in efforts to "Pretty it Up" seems to me incredibly STUPID, because it will produce waste products no matter what we do...