After looking at the descriptios/literature of each, the impression I got is that the ACS shifter was designed with the 3 series based cars in mind. It replaces the whole top piece to raise the shifter up to correct the shift linkage angle instead of merely inserting a spacer like the UUC kit. According to the UUC site, the 5s don't have the angle problem, as evidenced by the absence of an ERK for the 540s. It is only listed for the M5. IMO, the ACS kit would be a waste of money, as it provides a fix for a problem the 540s don't have.