Had this with a divertor valve on a Main combi, took GC number away with me to order the part and merchants came up with 3 different divertors! Rang tech support and they said they had three different variants during production and the only way they could tell me which one I needed was to be be stood in front of boiler and describe it to them! Could be a similar thing with your PCB
The difference is not really noticeable. But there's different boards for different serial numbers. Before and after a certain date which is identifiable by the date read from the serial number first 4 digits. So for example a 28kw duo tec built in the 20 week of 2009 will be CAC0920XXXXXXX
The difference is mainly due to the diverter valve, the old black diverter valve head is a more powerful motor than the white and black.
Either way the new pcbs both are vastly improved and come with brighter displays.