Chevrolet Repair: 1993 Chevrolet 350 Suburban

Question
I have a 1993 Suburban with a 350. It has 115,000 miles and when I bought it it smoked(blue) alot and used alot of oil. I had the intake manifold gaskets replaced and was told the old ones were hard and cracked. Oil consumption and smoking was reduced but at times will smoke alot and other times nothing.At times it will blow black smoke and bog down as if the fuel is to much. I replaced the egr valve and sensor,temp sending unit,o2 sensor. It runs great smooth and good mileage. Could the catalytic converter be damaged from oil consumption.It does not smoke upon start up. ???

Answer
GOOD MORN JIM, YES JIM ALOT OF OIL GOING INTO THE CATS WILL HARM THEM..BUT THIS IS NOT CAUSING THE BOGGING DOWN AND BLACK SMOKE COMING FROM THE EXHAUST SYSTEM...BLACK SMOKE AS YOU SAY IS A RICH CONDITION. THIS MAYBE CAUSED BY A BAD COOLANT TEMP SENSOR, MASS AIR FLOW GOING BAD.. SOMETIMES 1 OR MORE O2 SENSORS CAN CAUSE THIS AS WELL...I KNOW YOU SAID YOU REPLACED ONE...
GET THIS SCANNED ON A GOOD SCAN TOOL AND CK THE DATA CHART ON THE SCAN TOOL TO CK FOR ANY POSSIBLE PROBLEMS. THERE ALSO MAYBE A PROBLEM WITH THE PCM STARTING TO FAIL..[POWER CONTROL COMPUTER.]AS FAR AS THE BLUE SMOKE THIS IS FOR SURE A BURNING OIL PROBLEM...MORE THEN LIKELY THE VALVE SEALS AND GUIDES ARE GOING BAD....TO CORRECT WOULD NEED TO PULL THE HEADS AND DO A VALVE JOB,NEW SEALS AND REPAIR THE GUIDES...HOPE THIS HELPS YOU AND GOOD LUCK TO YOU,,,TOM