Volkswagen: motor losing compression, leak down test, compression test

Question
have a 1993 jetta 3 csl 1.6 .recently overhauled my engine and still losing compression .rebored the block 20 thou . schemed the cylinder head [changed the valves &stem seals & guides ]

Answer
One easy test is to shoot a small amount of oil into the cylinder and then perform the compression test again.  If the compression comes up, then it's the rings not sealing.  Otherwise, it's the head seal and/or valves.  
A better test is the "leak down" test.  This process is kind of a compression test in reverse,  It pushes compressed air into the cylinder at around 80 PSI.  The cylinder should be at TDC and the crank must be held in place to prevent the piston from moving.  Usually you need to find a properly equipped shop to do this. See this wiki article:
http://en.wikipedia.org/wiki/Leak-down_tester