Originally Posted by MaDMaXX

Yes, that's how i understand what you did.

The point i'm making, is that the SZ map doesn't contain the "change" to the spark advance. Therefore, having had the Church tune on the car (which does contain the spark advance) and *then* putting the SZ map back on (which doesn't contain the spark advance details) The end result would then be that the spark advance would remain the Church setting even though the rest of the map would be on the SZ settings.

That's why i suspect you wouldn't see a change when going back that way (Chruch to SZ)