Another thought to supplement Roy is that you could have an exhaust restriction. Check for a possible restricted catalytic converter.
The system is old EEC-IV Ford processor strategy. There is a Ford specific diagnostic connector that plugs in under the hood. Indeed - how did you check the sensors? I have to say that this is not the easiest vehicle or system to pull a datastream or valid parameters for...so...get in touch with a solid tech with good know how and diagnostic equipment. Good luck.