If you own a 123 chassis this kit can help you solve a lot of common vacuum related problems. If have not not experienced any yet, I can guarantee you will. Vacuum related trouble is one of the most frustrations in owning these cars - especially diesels. This kit includes my two vacuum troubleshooting and repair guides and our vacuum hand pump tester all in one money saving package. This will allow you to trace vacuum source problems starting at the pump and fix pesky vacuum door lock issues. The manuals DO NOT cover vacuum issues with the climate controls under the dash.