The question should be why bother, if it is mapped correctly/decently it won't be needed or of any benefit, I can get 40mpg on greys and 0.97% co idle on mot with 137ppm on a 200,000K mile engine(now being rebuilt).
I have CL on my ecu and never use it, even though it is a press of a key on the laptop away, tried it, better without.
tabetha