If it is just the seat locks you are having problems with, the first thing I would do is unhook the line under each seat and use the MityVac to apply vacuum to the diaphragms directly to see if they work and hold vacuum. There are two per seat connected in parallel, and if one leaks, they both won't work. I bet you have at least one bad diaphragm, as the rubber rots out with age. You can also use your MityVac to see if you have vacuum from the engine at the connection with the engine running and doors closed.