DML FAQ : Engine : Idle Trick (Works better than blocking/disconnecting IAC Solenoid)
For those with 5-speeds (or just want to keep the idle down a little bit when tapping the brakes or putting it into gear, you can simply disconnect the "Brake Sense" Circuit on the WHITE connector (at the PCM) - #C24 (White/Pink). You can cut it, but recommend just taking it out of the connector in case you want it back.
The PCM has logic in it that raises the idle slightly in Reverse and when you step on the brakes. This is why some people notice the idle go up a little bit when stepping on the brake pedal (more noticeable on manual trans than on auto...but same logic in in there).