Check MVB 125, that should be the fuel trim reading on a '97. Start the car from dead cold, well as cold as it can get in this weather, and keep an eye on the intake air and coolant temp sensors to make sure one of them doesn't have a dead spot in it - you may have to resort to the DSO.
Also, do the residual pressure test in ELSA, that'll let you know if you have an injector that's leaking down or if the check valve in the pump is bad. If it turns out to be the pump check valve, you don't have to replace the pump. You can get an external check valve to install in the fuel line. There used to be a tech bulletin that had the info so check in ELSA in group 20 and see if it's still there.
