Using a wider fov will make you slower. Yeah narrow will hurt the sense of speed big time, so long you are not using either triple screen or Virtual Reality which btw needs to be said too, but will increase your lap times dramatically as well, even on single screen. That is the nature of simulators.
Also, if FoV slider isn't available in GT7 on a PS5 with such porwerful cpu/gpu, then Yamauchi's case when it comes to the simulation department will jump in from laughable to definitely grotesque.
On a side note, arcade racing games with an also very low fov like Driveclub where in third person you see your car in a glorious big shape in the middle of the screen, and at the same time holding a sense of speed as if you were running high fov (old ps1-ps2 style of third camera view), has been one of the greates achievements imo in what it comes to pure fun and addiction to speed, all combined with more or less believable physics (hardcore mode of course, but in this mode i use bumper camera not 3rd person view). I still don't see me quitting on playing Driveclub even after all these years combined with all the other sims i play, not even when GT7 hits.
Yeah I mean the greatest ps4 racer still is, and probably will continue to be Driveclub. But hey bit off topic here yeah, but not in the FoV conversation..