ATI Supercharging

[Doug Gubbins]

Help!! Seeking engineering expertise:

I'm running an aftermarket intercooled supercharger on a 1.6L Mazda Miata.
Max boost 12psi, using 93 octane fuel, higher when I can find it. The system
uses a boost-controlled variable fuel pressure regulator and an MSD spark
retarder.

This past weekend I clogged up, fused, or melted the honeycomb in my
catalytic converter. I haven't yet inspected the cat, but I believe it's
heat damage. I'm told this could have been caused by one or more of the
following: 1) running too rich most of the time, allowing unburnt fuel to
reach the cat, where it ignites, 2) running too lean at boost, causing
excessive combustion temperature, 3) too much spark retard (the MSD unit's
over-compensating), 4) too much spark advance (the MSD unit's not working at
all--but I haven't heard any knock).

Should I be able to glean any clues from the appearance of the cat? For
example, if the face of the honeycomb is fused, would that indicate
condition 2, rather than 1? The exhaust system does have an oxygen sensor,
which I am told outputs a voltage between 0 and 1v--lower is leaner and
higher is richer. Should I be able to monitor this to diagnose the condition?

I am considering replacing the MSD spark retarder with a knock sensor
package that also contains an LED oxygen-sensor monitor. But it isn't cheap.

Can one of you engineers enlighten me a bit and maybe prevent my throwing
money away on a solution that might not be fixing the basic problem? Or how
to tell conclusively what's going on here?