Exhaust Gas Recirc.Flow Insufficient Detected
Probably needs a new EGR valve, check the vacuum line going to the valve before you replace it.
99 Chevy Silverado Z71 6" rough country lift/W 35" tires, 4.10 gears, (4.56 soon) S&B CAI and a flowmaster super 44 exhaust.
"Never argue with a fool, they will lower you to their level and beat you with experience." My personal motto.