What may cause a 1986 Mazda pickup rebuilt carburetor to not run right and cause an uneven idle?

Well assuming the carburetor is set properly idle wise with a meter and all the normal tune up things are in KNOWN good condition.My suggestion is clean the egr valve under the carburetor with carburetor cleaner and note the position of the gasket on it for reinstall purposes.When cleaning it use some sand paper or a small brush to remove the carbon buildup.It has one vacumm line,one electrical connector going to it with 3 ten millimeter bolts that hold it on.If the idle is still crappy I would suggest a new map sensor which is mounted on the passenger side fender with a vacumm line and electrical connector on it.And the tune items like plugs,wires,cap,rotor button and even the oxygen sensor are critical.Hope this gives you some insight into the issue.