Exhaust side specs up tomorrow.
Came across this on my travels:

''VW 16v head:
The VW 16v head is a performance nightmare. I think VW introduced the
head merely to say they had one, as they obviously didn't care about
performance when they designed it. VW began design of the 16v head
about 1980. It went through various metamorphasizing phases before
it was released. On one version, the exhaust cam was gear driven,
but VW ultimately chose chain drive because it was the quietest way
to drive the exhaust cam. (The quietest way they would consider;
they obviously chose not to allow the exhaust cam to be belt driven
with the same timing belt as the intake cam...which would have been
the quietest by far.) According to my sources, VW was planning to
introduce the head as early as 1984-85, and some 80000 units were
produced. Then it was discovered that some engineer forgot to design
water in the casting around a pair of exhaust valves. Overheat =
cracked head ==> junk 80000 castings <==> put the program back a
couple of years.

Before the head came out, rumors were circulating as to its design
characteristics. All of us in the high performance business cringed
at what we heard. We heard that VW had designed the head with the
exhaust valves top dead center over the combustion chamber; the
intake valves cocked over about 20 degrees. We said if that was true,
the head was junk. We couldn't believe VW (read that ANYBODY) would
introduce a high performance head with such awful flow characteristics.

When I saw my first 16v head (off the motor), all my nightmares turned
into reality. Actually, it was worse than I thought. The exhaust valves
were top dead centre, but the exhaust ports exceeded a 90 degree bend
to allow the gas to exit. This head was obviously not designed for
performance. The valves spacing is too close together, thus putting
in bigger valves would be near impossible. The only possibility of
obtaining higher performance was porting and polishing.''