Walter: It is very difficult to find this optimal carb temp without and EMS, but with one it is very easy.
In the IO engines, the F:A ratios are balanced by tuning the injectors (GAMIjectors).
So my understanding then is the average PA28 or C172 pilot cannot do LOP operations with the aircraft equipped as it came from the factory. At the minimum there needs to be an engine monitoring system fitted and if fuel injected the likes of GAMI injectors need to be fitted too.