So the game ran perfectly fine until the latest game update which brought in this horrible stuttering / hitching every few seconds. especially while driving. i ended up trying everything from driver updates to clean installs nothing seemed to work until i tried this:
i fixed the hitching / stuttering crap.
\Documents\Rockstar Games\GTA V
and delete settings.xml
restart GTA5 you might get an error telling you to launch from the GTA5.exe just click ok / start GTA5 in normal mode. (I think it has something to do with generating a new .xml file)
This completely fixed my stuttering issues after the new update.
Just posting this here for exposure. if it helped me out, it could possibly help you out.
Comment below if this fixed GTA5 for you.