First, sorry for my english, i‘ll do my best to describe my question:

Had my gearbox in my TD6 rebuilt (stronger parts) at 140.000kms when it broke.
Previous owner fitted a tuning box when car was new. I always have a slight
vibration from drivertrain when i accalerate in 5th gear between 80-100kmh, hardly noticeable.
Only when you accalerate harder or uphills (whitout gear shift back to 4th). Now, for testing in disabled
the tuning box, now vibration is gone.

Is this something with the torque converter lock up clutch? As its a tuning box, could it be that the gearbox ecu
has no clue what is happening (real torque/ps)? Any experience from users with a real remap?

Thanks!!