what are you trying to accomplish? what is your car? do you have a way to monitor engine load right now? do you have a scangauge? are you talking about at idle?
the reason I am asking these questions is because I have an idea of how to do this but I am not sure why you would want to do this. you could monitor your load at idle. cut the car off. splice a small value resistor in it and see how it changes. gradually increase the resistance value until you get to where you need to be. you can get resistors at radio shack for 88 cent for 5 I think. also you could get values that would allow you to combine and make endless values. this will take time but depending on why you want to do this it may be worth it.
why are you doing this again??
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