A relationship between the mass-loss rates of AGB stars and the chemistry within the circumstellar envelopes that this process creates has not been thoroughly investigated. We have obtained high spectral resolution (R > 60,000) observations with the Echelon Cross Echelle Spectrograph (EXES) on SOFIA of a small sample of C, M, and S-type AGB stars. The mass-loss rate of this sample ranges from 10-7 to 10-5 solar masses per year. We have focused our observations on two spectral regions that permit us to to sample several molecules exceedingly difficult from the ground and/or with no permanent dipole moment: water and methane at 7.5 and carbon dioxide at 13.5 micron. We will present early results from this project.