for an idea of what you might find you can do an easy cylinder leak test.
you can buy a tool to do it but i made a simple one that does the job for free.
get an old spark plug and remove everything above the nut part so you are just left with the thread and nut.
next weld an air-line fitting to the top part just above the nut.
you should now have something resembling a spark plug but instead of fitting a plug lead to the top you can connect an air-line!
now to check each cylinder in turn you turn the engine over to tdc, one cylinder at a time
when you have it there (make sure that it is on the firing stroke for that cylindre, not with the valves "on the rock") then lock the flywheel in place. next screw in your new adapter and attach an air-line to it.
you will then find out where the compression is going.
from the oil filler cap, it's going past the rings.
from the exhaust it's coming past the exhaust valves
from the intake it's coming past the inlet valves.
at least then when you strip it you will know where to start looking.
be aware though, 16V engine parts are pretty expensive.........