If it's chipped then it may be the fitting of the chip in the ECU that has a dry/bad solder joint.
The chips were fitted to a spare location on the board that required de-soldering of 28 PTH's and fitting the chip or a chip DIL holder.
A link resistor is then cut to run the remapped chip instead of the on-board chip.
I would suggest you check the solder joints as I have seen very bad fitting in the past.
You can also add the removed link, to run the base board and standard map.
Jap mapping on the ECU I've seen was very poor and very aggressive, especially for UK fuel. Some of them I am surprised ran at all.
Below is a piccie from my old website :
