This is not for original 3rd gens but folks may find it helpful
Reference Service bulletin # 10-06-01-008M
Aluminum block RPO's LH9,L94,LZ1,L99,LC9,LH6,L76,L92,LFA
Iron Block RPO's LMG,LY5
My 2007 Avalanche w/ 86,000 had oil consumption issues. Spark plugs 1 and 7 were oil fouled. These are two of the four cylinders that deactive during Active Fuel management ( V-4) mode. After researching the issue others have similar issues. My truck also has had the valve cover on the drivers side replaced per the referenced service bulletin.
I bought the Diablo Sport Sprint ,which deactivates the Active fuel management ( V8 mode all the time now). So far so go. Oil consumption is much better ( 1500 miles + with no oil consumption)
If you have and LS motor with AFM, watch your oil consumption!