The Sable Saga Continues.

1987 Sable 3.0. I'm learning a lot with this car. It had troubles. Step by step, inch by inch, I have figured them out. Many parts have been replaced, rebuilt and/or repaired. At this point it runs slightly rough, the tach occasionally hangs at 1700-1800, it shows a code 89 (torque converter lockup), it is down on power and is only getting 11 mpg. It got 22-24 before. Idle is high, but the code says it is out of range low. It shows a knock on the code reader, but it is not equipped with a knock sensor. It used to show an EGR fault even though there is no EGR valve, but that's gone now. Any thoughts on how to proceed? Temp sender, map sensor, o2 sensor, TPS, IAC, radiator, upper manifold gasket, PCV valve all new.