Maybe my description was confusing (you will have realized I am not a native speaker...). Anyway, the output in my case is a change of the flap position. I don't want it to be the flap position itself beccause I assume that the flap's position will not result in the same temperature every time (it will rather depend on how much charcoal is glowing, ambient temperature, "meat-load"...). So, high deviations are to result in higher (or faster) position changes (or 100% of the maximum allowed change) while slight deviations will cause only small corrections.
Anyway, I will change the tunings to smaller values, leave the sample time untouched and see what happens...
Axo