The high idle mod is actually installing a toggle switch in the SEIC (stationary elevated idle control) circuit wiring. It only takes about 30 mins to complete and is a cheap mod that you will find yourself using more than you would think. It helps to warm the truck up quickly, and also is good for elevating the idle to get the A/C cooling better. True your truck will idle up without the mod but there is no control of when it kicks in, and this will allow the idle to pick up to 1200 rpms. Heres a link...High Idle Mod
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