If he defeated the EGR valve by closing its passage, the car more than likely will not pass a smog test, reguardless of any performance increase. When they check the ERG as part of the smog test to verify its proper operation, the non-functioning status will be obvious. That will be a guaranteed failure, so don't forget to get a new EGR gasket so you can restore the proper condition before the smog test. I wouldn't be surprized if one side of the valve passage fills up solid with carbon- and that stuff is hard as a rock- when you do that little cheat.
