David,
are you/is your 2.1l having any of these?

   1. A vacuum reading that cycles up and down slowly could indicate a fuel
   mixture problem from improper carburetor or fuel injection operation.
   2. Low vacuum readings may indicate intake valve, manifold, or carb
   gasket leaks including internal or external manifold leaks.  Spray carb
   cleaner around suspected areas to test for leaks.
   3. Plugged catalytic converters, stuck heat riser valves, plugged intake
   crossover heat passages, crushed exhaust pipes, plugged mufflers, (check out
   that mouse nest in the exhaust!), and similar restrictions will usually lead
   to very low vacuum readings.
   4. Excessive carbon in engines or those that did not get their oil
   changed often enough may result in sudden vacuum reading changes when valves
   stick. It could happen at any engine speed and may temporarily cure itself
   by quickly changing engine speeds.
   5. Lower vacuum readings directly related to engine misfiring may be a
   result of a burned exhaust valve.
   6. Constantly changing vacuum readings at low engine speeds may indicate
   a problem with worn valve stems, guides, or seals. Higher engine speeds tend
   to temporarily cancel out this problem.
   7. High-speed vacuum readings that change may be a result of broken or
   tired valve springs, while low engine speed vacuum readings tend to be
   constant.
   8. High performance or race cams tend to result in lower vacuum readings.
   9. *Make sure that the cam and lifters are matched, (solid/solid,
   hydraulic/hydraulic, roller hydraulic/roller hydraulic, solid roller/solid
   roller), etc. Strange things happen when these items are mismatched,
   although some will actually run that way. Cam indexing/timing will also
   affect these readings. Also check for sloppy timing chains, and improper or
   changing ignition timing.  *

bob