I recently had my 383 motor put back in, and the mechanic that did the installation said the engine shop did not put the EGR valve back onto the engine. He has a vacuum hose that he couldn't install. Is this the reason why I can smell my exhaust when I stop at the lights with the windows down? Also the car spits out a lot of black smoke which is dirtying up my bumper. Is the EGR critical?