Check your PCV valve housing. There is a spring and two o-rings, one on top and one on bottom. IF the spring is broken or missing, or one of the o-rings are missing or torn, the resulting vacuum leak will cause an Insufficient EGR code to trip. The MAP sensor sits on top of the PCV housing, and the PCM uses MAP sensor signal to monitor EGR efficiency. GM makes a repair kit, part #89017274 that consists of the PCV valve, spring, both o-rings and the top piece that the MAP snaps into. It costs $20 from a dealer.