grand marquis codes

hey i ran a code reader on my 91 grand marquis and came back with codes 23,34, and 81. I know 23 is the TPS and 34 was a senser on the EGR i believe, but 81 is air management 2 circuit failure, i have no idea where that circuit is. The car is just running with an irratic idle, usually resulting in stalling out. Any helo would be great, thanks.