I thougt the egr spacer has a barb fitting on each side of it. You could cap it off with a rubber cap and that's about it. It sounds like he is talking about the threaded NPT plugs on each side of the gt40 inake beside the egr spacer. These are just spare ports to be used for vacuum or nitrous oxide. As for blocking the coolant lines off, that would be a bad idea if the EGR is still functional. With the lines connected the egr spacer will stay around 230 degrees if you remove the coolant lines to the egr and it still has hot gasses going through, it will heat up above 300+ degrees. One of the tech manuals I have they did a test with a thermocouple and found this to be a fact that the intake egr spacer will be hotter without the coolant lines.