Is the stock trigger on a Evo 1-3 supported by the firmware?
As far as I can find, it doesn't look like it would be supported..
Is this the 'egg beater' crank based trigger?
That is a good question..
It's not my car, but I did have a quick look on the engine when it was swapped and as far as I saw then, it didn't look like there was any trigger on the crank.
Could it be that it only have a cam driven trigger?
I'll have a look once more to be sure how the trigger looks!
A lot of earlier Japanese cars had EFI retro-fitted, so they modified distributors rather than redesign crank assemblies to add triggers.
It seems that they've only relatively recently moved over to crank triggers - probably as a result of variable cams.