I have a '93 with a 5.0. I pulled some codes today and need help figuring out where to start.

327- EGR feedback signal is low/was low EVR or PFE
637- TOT sensor is/was high or open -- Transmissions
311- Air system not working. Single right or rear H02s- Air injection
632- E4OD - Transmission control switch (TCS) should be cycled once between engine ID and goose test.