My 97 SL320 ( M104 3.2 inline 6 cyl with Bosch ME 2.1 injection ) has throttle by wire so it does not have a cruise actuator / computer.

My 91 300SL - 24 valve ( M104 3.0 inline 6 cyl with Bosch KE injection ) has a throttle cable and a throttle body that has a servo motor override ( for the ASR system ) but I have no idea if the same motor provides cruise. In might be a few days but I'll have a look.