Hi!
Under Detail stats - uUility there is Engine idle. How is this calculated? And same with torque curve…?
Anyway, massive respect to developers, awesome work 
Engine idle is calculated from various engine parameters like cam, engine capacity, number of cylinders and fuel system type. You can see your engine idle number in the engine power/torque graph, it’s the starting RPM 
Hm… ok you gave me some clue but I still don’t know how to improve my stat so I guess it’s now trial and error time
Not much to do for you there… lower idle gives better score in utility (obviously) as you want to tow things. Now you just need to figure out what makes lower RPM idles 
not that hard either.
A few hints, typically lower number of valves (they are working on a better implementation)
Long tube headers
Smaller exhaust
Lower cam number.
Thanks!