Then there's another potential problem.

EGR limites NOx by introducing inert gas into the system. Those with older engines who block off the EGR valve do not have catalysts in their exhausts. We do.

Even if you ignore the smog problem if everyone were to do such things to their cars, are there potential problems for the catalysts? That part is expensive enough that cleaning the intake once in a while seems cheap.

Sorry, guys, but I'm not experimenting with my EGR setup.