Got some doubts but a few of my thoughts.....


As long as the oxygen level ratio to fuel remains the same then
combustion wont be affected depending on how much is added.

However, the low CO is beacuse it is a measurement percentage of the
total mixture volume that the N2 is now taking extra place up so that is
miss leading I think.

Higher cyclinder pressures caused by less space in the cyclinder effectively
raise the CR so may have some benefit but may peak as cyclinder temperatures
rise and cause negative effects.

I have heard also that N2 mix does increase the knock threshold to a point.

As for saving fuel without decreasing performance - NO