2002 Camaro idle speed adjustment?

2002 camaro with V8 and 26,000 miles that idles around 600.
Is there any way for me to bump that idle up?
The alt. Is not charging enough for all the components at that low of an idle.
I adjusted the set screw but after the car was turned off then back on the computer reset the speed back down around 600 again.
Is the low idle speed my issue?
Alt has been replaced twice and still test good.