Here's a low-tech solution.

 

Here's a low-tech solution.

It could even have a string of blue LEDs attached to it.

 

GND maybe this is what you are lookin for.. states for 5.7L RAM
You should be able to modify the system by yourself though..
http://www.americanpowerinc.com/high-idle-controls/

 

When someone says "Why climb a mountain?" and someone else says "Because it's there." That isn't truly a good answer. One inescapable fact is that you are going to set your own course. Come what may; and consequences be damned. Us "OLD" people, and I certainly qualify for that title, have a greater wisdom and wealth of experience to draw from. Asking "WHY" you want to do something sometimes helps us help you. Other times our "WHY" is to open your eyes to something you may not have considered.

I don't mean to offend you. Not anyone. But sometimes a person needs to be told a blatant truth with the hope to steer them in a better direction.

You want to put a high idle device on your car. OK. Go ahead. Like I said before, I've given you all the help I know how to, both with circuitry, be it a limited knowledge base, and with some - pardon me if you take this the wrong way but - fatherly advice. But I remember ignoring my fathers advice. I also have paid a price for not listening to his wisdom. Not saying I'm wise, just saying I lament not listening when I had the opportunity to. But as to why I'm still trying to stop you from possibly harming yourself, it's probably because I'm a fool and sometimes I run a fools errand and think something good may come of it. Nevertheless, like I said, you know enough to make your own judgements in life. It's your life. Live it as you see fit. But don't be so quick to discount what others say. Even if in the end you don't accept what someone offers you in ways of wise advice, at least if you take the time to consider it you may just expand your horizons a bit just having considered the possibility. Like I said, even if you disregard it in the end, you'll be richer for having given the matter a little more thought. Since I'm not the only one with words of caution then maybe there's something more to what's being said to you. Maybe. But to find that out you might consider it. Even if you don't take the pearls of wisdom.

Done all I can. 'av'a g'day mate.