You sure you hooked up the vacuum to the egr properly? It doesn't get a vacuum line from the intake. There is an egr switch (harness plugs into to it too) on the firewall that gets full manifold vaccum; a separate vacuum line runs from the switch to the egr valve. The valve only gets vacuum from the switch when the computer tells it do provide vacuum - at part throttle. At idle, and w.o.t. there should be no egr valve operation. If you pull the vacuum line off the egr valve at idle, nothing should happen. If you hooked full vacuum to the egr valve, that would screw things up and impact drivability.