Whether to use the original ECU or a newer ECU, if it is generally used for civilian refitting, I personally recommend using the original ECU for refitting. Because the function of the original ECU is very powerful, and its program is developed after long-term data accumulation and countless tests by the engineers of the manufacturer. It can protect the engine under any circumstances, and there will be no fault codes and warning lights. There will be no rejection problems that occur when other systems such as ABS, anti-skid and anti-theft systems work together, and it will not delete some important functions on the car. On the other hand, the cost of retrofitting is relatively low.
Regarding the degree and adjustment style of ECU modification, from the perspective of performance modification, ECU modification is an indispensable link. The ECU can help the engine perform its best mechanical function, but it cannot go beyond what the original design allows. For example, when some professional racing teams develop the engine of a racing car, they first design the matching of mechanical parts such as camshafts, pistons, and connecting rods, and determine the data such as the compression ratio and maximum speed of the engine before considering the ECU. Because there is no powerful engine, no matter how “capable” the ECU is, it is just a waste of effort.