"It had a similar problem and my shop sent the module to someone who checked it"
Jesse it correct in that the most likely problem is a bad cruise control module.
The vacuum actuator and its hookups are rarely if ever the problem.
For more info, read here under "Cruise Control Systems":
TECHNICAL
And if the module is bad, call Pelican Parts even if the module is not shown in the catalog,
as they have many sources for Porsche parts.