How to fix code P1381 Camshaft or Crankshaft sensor?

The car has a huge lack of power. When the a/c is turned on, it places a heavy load on the engine and it also chokes as if it wants to cut off. The car also has a rev limit of 3000rpm. Since have this problem I have replaced the distributor with a used one purchased from ebay. The problem still exists. The P1381 code is still there. Is the cam sensor actually in the distributor or is it attached to the crankshaft position sensor? What would cause these problems and how can it be fixed?