well after much stuffing around, all old parts are within specs but replaced them anyway, replaced new tps and map sensor to no avail..

at this stage im just going to disable the lock up..

97 NL FAIRLANE IS FIXED !!!!!!!!!!!!!!! :
Well after over a year with this problem of the converter locking/unlocking I have nailed it.
Due to it getting worse and at cruise speed constantly switching between locked/unlocked, I thought I might check for any codes from the ECU again. Up comes code 113 ( faulty IAT Sensor ) so off to the local wrecker and $5 later I have a second hand one. I then measured across the two terminals of it Tuesday morning and its resistence was 40K ohms( at around 15 degrees celcius ). Due to it being under the throttle body and hard to get to I decided disconnect the plug to the IAT and put a 39K resistor in the plug. After testing for the last 4 days & it running perfectly I have now put in the second hand IAT Sensor and all is fixed. ALSO the car used to sometimes start and stall - this is fixed. ALSO the revs used to go up above 1000 when I stopped and put the transmission into park - this is now normal.
I hope this helps out the other people with the same issue.
Thanks for all the other suggestions from FORDMODS members.
Cheers,

Also to add to that, The 40k ohms was on the good IAT Sensor from the wreckers. After removing mine it measured at around 300k ohms ( way out of tolerance ).
I cannot believe it is the same car now. Transmission is working PERFECTLY !!