Bosch ignition timing and pinging

["Tom O'Neil" <tomoneil41@xxxxxxxxxxx>]

My 1984 Spider is pinging on acceleration, otherwise it's great. My fuel's 
good, the vacuum sensor responds to a hand vacuum pump, and I'm fairly 
certain there's no carbon problem. Here's my (dumb) question:

Since it's not a purely electronic system (i.e., there's still a mechanical 
distributor), what exactly does the Bosch ECU do to vary the ignition 
timing? Does it rotate the distributor? (I don't see any electrical 
connectors down there.) For what it's worth, last summer I replaced the 
catalytic converter with a straight pipe. Could this be influencing the 
manifold vacuum enough to throw the calibration off?

Thanks to all!

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