Thanks very much for all the detailed feedback and answers fellas; I now have a much clearer understanding of how the Kev Mod works, as well as a better understanding of the closed-loop/open-loop modes and when they kick in.

So, it looks like I'm going to be ditching the Nitro-X in favour of a Kev Mod. As I suspected, a significant disadvantage of the Nitro-X is that it dispenses with the IAT and therefore disregards the ambient air temp. As you've pointed out, the Kev Mod takes that into account by wiring the two together in series.

I briefly considered rewiring the Nitro-X in series with the IAT, but the resistance values aren't suitable for that, plus you can only tweak the value in steps anyway, not continuously like the Kev Mod. Way to go, Kev!!

Look forward to hearing how oldf4rt gets on with the plug-n-play O2 eliminator - I reckon I may end up going that way too.