The Mighty Vac will evacuate your vacuum system for diagnostic work. I've used mine for over 12 years with great success. About $30-$35 for the basic kit at NAPA, Pep Boys, O'Reilly, etc. Make some calls to locate one.
America: Land of the Free!
1977 300D: 300,000+ miles
American Honda: Factory Trained Technician & Honor Grad.
Technical Advisor to Am. Honda;
Supervisor of Maintenance largest tree care co. in US for offices in Tex.