If it locks on the street with the chip, then try manually locking the car with a paperclip or piece of wire.
If you insert a piece of wire to the aldl connector below the radio at the upper left to the upper right, this will lock the convertor in 2nd 3rd and 4th.
Go drive the car with that clip in there(touching the brake pedal will release convertor being locked) and hit mid 2nd gear well into 3rd gear.
If its locked, you will feel it immediately, at wot see if the conv is still locked.
Could be that its trying to lock but the conv wont hold it and its slipping.
What convertor?
BW