Fibrous nonwoven mats comprising polyetherimid fibers and a binder comprising a resin and an adhesion promoter, and method of making the mat are disclosed. These mats have several uses and are particularly suited as facer mats for fiber reinforced thermoplastic thermoformable materials. When used as a facer, the mat bonds to the thermoformable material and provides a resin rich outer layer and facilitates bonding to a decorative cover.