Is There a cheaper why to bypass the cats on this car than putting new ones?

Remap the computer for blocked cats, but it runs normally? That's almost a contradiction, there's a way to get cat efficiency as well as back pressure. I personally think there's something missing here, maybe another opinion wouldn't be a bad idea. I would also make sure that the data can be read by their equipment and the technician is familiar with Mercedes. If cats are required, there are several options for replacement that do not require "remap". Bad feeling on that diagnostic, again just my opinion.