If you are like me, you have GTAV and rushed to use the first person mode only to find shockingly poor FOV levels even when the slider is maxed out. Well there are already mods to fix it, here is one I found as of now https://mega.co.nz/#!4AQGzJjB!9mclkHp43fbGSOLhD8d-mC4CNes-9QeXVOEebOD4txk It is rough around the edges, I admit, but it does what it says. If I or anyone else finds a more polished mod, I will gladly edit this post and put it in for your convenience.
Fair warning though guys, Rockstar has not said if they will allow this or not, so it MAY RESULT IN A BAN AT THIS TIME. Read more here http://www.pcgamer.com/gta-5-mod-allows-custom-fov-in-first-person-mode/
I read that this morning. Since the mod is also activated online and changes memory settings Rockstar might not allow it and could possibly result in a ban as @twRage96 has said.
i expect this mod to be included in the next update, because people have complained about the fov and most pc players will probably download the mod