High idle when cold is normal. This is controlled by your IAC, idle air control valve. After warmed up, it should drop down to normal idle, which for your truck is 800rpm.

Your idle adjustment screw is on the top of your throttle body.

If you still have high idle problems, it could be a vacuum leak, PCV plugged, or a few other things.

88 4R, 350 V8, R150 5 speed Sold <...uot; />
97 4R, stock, daily driver
98 Sienna, kid and dog hauler, wife's ride