LOL...that is true.

The facts are pretty simple here. NOx became the big target in that period and lower compression, egr, and retarded (reduced) timing were the tools available in those days to try to reduce levels and the implementation was very crude by today's standards given the lack of computer control.

All the manufacturers had similar versions because the science was the same for all. It should be a moot point today as most of us are after performance and are not running timing curves similar to what the factories had to impose to achieve the reduction.

Performance was a secondary consideration and the results definitely reflected that.