If memory serves me correctly, all the ecm did was work the lockup on the converter. I had a 1988 Mustang LX with that transmission in it. I bought the car as a basket case. The PO said he was having tranny issues and pulled the original and replaced it with a salvage yard unit. His issues didn't go away. He started to pull it back out and stopped, leaving it as is. I bought it from him that way and put the car back together. His problems came to light very fast. The car would actually stall as soon as I accelerated. Took me a while to figure it out but the ecm was causing the converter to lock up right away, killing the engine. I unplugged the wire from the transmission and my wife drove it like that for a year. The lockup is good for around 300 rpm or so on the highway. Didn't make much difference without it. About a year later the transmission started slipping and I swapped it for a T5. Once i pulled the A4LD I found out that the locknut on the high gear band had come loose. That cause the adjustment on the band to loosen up and caused high gear to slip. The transmission was still good and I sold it. Long story short, while 300 rpm would be nice it doesn't make a massive difference for fuel mileage, if that's what your after. If you do a ton of freeway driving, you could always install a toggle switch to work the lockup. Just remember to turn it off when slowing down lol. This is just my opinion for what it's worth. I'm sure someone else will chime in.