A stuck diverter valve just downstream from the smogpump can cause an issue......usually its something causing a lean reading that will cause the cars computer to compensate.
or a broken bolt like i had in my lower intake, causing a little water and a lot of black smoke out of one pipe, 95 dual pipes v6 with no h or x pipe. take the vacuum hose off of the fuel regulator and smell the hose for gas, if it smells like it, replace the regulator
an overly rich condition can sometimes be cause by an overly lean condition, your comp will adjust your fuel trim accordingly and sometimes it can mess your mixture up big time.
how about malfunctioning/disconnected ect, failed ecu, dirty mass air vane, vac leak (lean to rich) there are tons of things that could cause it to "smell rich" are you running cats?