Depends what you mean by crossflash
By vehicle:
RS4 and S4 have differences (cam position sensor, intake flap), 512k vs 1024k won't crossflash, Bosch/Hitachi MAFs require different MAF maps, there are eeprom coding restrictions for some combinations, there are CANBUS differences for some combinations.
By ECU:
All 2.7t ME7.1 ECUs are physically the same except for 512k vs 1024k issues.
Indeed
I’m aware of the rs4 info
Also the maf differences. purpose of this is I have a riser chipped an a box and don’t want to boot mode every time I make a change.
Was looking for a cheaper alternative instead of the price markup for the m box and other a boxes