Oops, I'll go back and correct that last post. You already answered the question I left out, though: I wanted to know how you built your input circuit.

We use a slightly different configuration than what's in the Megamanual. If you replace the 150ohm resistor in the Megamanual's schematic with a 1k ohm resistor, the input circuit will be electrically identical to what we use. It's much more like the first circuit you mentioned, rather than what's currently in the Megamanual.

I hadn't thought about the ignitors, but you're absolutely correct: they're another major difference. We exclusively use the Bosch BIP373's and so far they've been great.

As for the Neon market, we supply them with the majority of their Megasquirt ECU's these days and of course, we only use the Hall/opto input circuit. Just like the 420A DSM crowd, we haven't been receiving any complaints from the Neon guys about spikes in their tach signal.

So, I suppose the list of things to try is:

* Change 150ohm resistor to 1k ohm resistor.
* Try new crank angle sensor.
* Replace Fairchild IGBT's/4G63 ignitor with Bosch IGBT's.