Well, I don't think any stock engine management system could handle that sudden of a change in O2 without any warning (such as intake P or mass flow going up) - its just that some engines are naturally more resistant to or tolerant of detonation so it doesn't matter as much.
Usually, stock ECU's of the late 80s thru 90's could only adjust fueling 15 - 20%; if you're running a 50 hp shot on a 150 hp engine, you'd need roughly 33% more fuel (more if you want it slightly richer for more cooling & detonation protection), which the ECU couldn't provide anyway. Plus, there's always a couple-cycle delay for the exhaust to reach the O2 sensor, for the sensor to react & tell the ECU, and for the ECU to start correcting. Plus, the knock sensor & circuit is almost worthless, so that can't even act as a band-aid until the ECU catches up.
It's not really a fault of the ECU, a 50 hp shot of nitrous is a bit more than it's been designed to take.