The more I thought about my problem, the more it pointed toward
detonation, as the only thing significantly different is the fact that I
had advanced the timing when I started flying n.a.  It was torture
working the last 48 almost straight without being able to test.

With the old turbo I followed the directions for timing in the EC2 guide
but did not trial any advance.  Tried to keep boost under 38"MAP but
once saw 45" without problem.  After the turbo broke I advanced the
timing with the EC2 to try to get more power and economy.  With the EC2
you can advance or retard 5 clicks (-5 to +5), each click is about 1.8
deg.  I ended up advancing all 5 clicks with some mild improvement in power.

So today I went and put it back to 0 clicks.  Ran the engine up to
40"MAP without loss of RPM.  Then I gave it 3 clicks of advance and lost
power at 35" MAP.  Down to 2 clicks and lost power at 38".  So I left it
there for the time being. I obviously can easily make changes as I get
more experience with the turbo.  38" is the most I plan to run for the
time being, and continuous will be no more than 32". It is also now
clear that as the engine got warmer, the detonation happened more easily
(at a lower MAP).  That is why on climbout It occurred despite the fact
that I had not changed boost - the engine got hotter.  Two clicks and
38" was at the hot end of the range.  There will probably also be
changes in this due to mixture setting and type of fuel.  (Current fuel
is Mutt - a mix of 87, 91, and 100LL)

This has been a great learning point for several reasons:
1) I now know what detonation sounds like - at least when it is due to
too much advance.  It may be different at higher boost levels, or when
it is primarily due to too lean of a mixture (at higher boost levels).
And that is merely an abrupt loss of power without loss of MAP.  I was
expecting rattling cans and firecrackers but the engine actually ran
very smoothly.
2) I now know that my rotary can tolerate short periods (long enough to
manually pull back the throttle) of detonation (at low boost) without
any apparent harmful effects.
3) I know what to do if this occurs again and I have some sort of
baseline as to where I can expect to see detonation.  I am very sure
that I want to avoid it at all costs at higher levels of boost as
detonation will likely be destructive then.  Yet, I don't want to be so
far out of the ball park that I am wasting fuel and available power.

The really nice thing about the EC2 is that it is SO easy to make an
adjustment in timing, mixture, or both.  When trying to impress my
Lycoming RV buddies this will come in handy.  In the time it takes them
to go to fine pitch on their prop, I can retard the timing a few clicks
and go to 45" of boost  :-).  Then in cruise I can advance the timing
again and still match their fuel burn - all while running MOGAS.

Thanks Tracy!  (and on the wish list is the ability to have a timing
map, or at least a few more transition points)

And thanks to everyone who piped in and helped me with this issue!